OUR PUBLIC SCHOOLS COLUMN

Otago Witness, Issue 3114, 19 November 1913, Page 72

OUR PUBLIC SCHOOLS COLUMN

FOR SENIORS AND JUNIORS. (Conducted by Magisteb, to whom all communications must be addressed.) [U agister will he glad to receive Nature note®, marked papers containing educational articles, diagrams, details of experiments, etc., of scholasth interest to teachers and pupils. Correspondents must use OSi.Y Onb side of the paper, and whether using a pen name or not, must send both NAME and address.! ONLY A WORM. “Taffy Secundus” sent rno a worm last week, and wants to know something about it. Perhaps in my “ Notes and Correspondence ’’ section some reference to it will bo scon; if not, all being well, I’ll have it identified for next week. Some weeks ago I had intended to give some notes i took of Dr Benham’s lantern lecture on JtVorms. Why, after hearing the professor speak upon these humble objects of animal life, one is almost inclined to go into ccotiicies over their beauty, and certainly over their usefulness. At that time, however, other matter pressed in, and one of rny little arrangements was upset. Though not giving any oL Dr Bonham’s lecture, I am giving- extracts and adaptations from an article, “Earthworms in Victoria,” in the July issue of the Victorian Journal of Agriculture, and written b.V Janet W. Raff, M.So., Government Research Bursar in the Biological Laboratory, Melbourne University. But let me preface my extracts by a note. Look at a worm and you will see. nearer one end than the other —the head end, though the ordinary observer can hardly distinguish one end from the other—a saddle or girdle. If the girdle is near the end the worm is a New Zealand native; but if approximating to the middle it is the descendant of an imported worm—an alien which is ousting the unassertive native. Earthworms in Victoria. “ Earthworms have been called ‘ ploughers of the field.’ _ They burrow through the earth, swallowing it, and absorbing as food any nutrient material contained therein; and their castings, continually brought to the surface, are blown about when dry, and thus spread over the surface of the ground us a line layer of mould. An enormous effect is produced in this way on the superficial layers of the earth. Darwin calculated that there were in one small garden of an acre over 53,000 worms, and . that 10 tons of soil per acre passed through their bodies annually. They were estimated to cover the surface with a layer of soil o.2in in thickness, so some idea of the important part they play in Nature may be formed. The soil is submitted to the action of the atmosphere, and the burrows allow of fhe free percolation of rain into the deeperlying parts of the soil. The worms live chiefly in the superficial layers of the earth; this is passed through and through their bodies, and is ultimately carried to the surface as castings.

“ Spring, and autumn appear to be the times in the year most favourable for casting, during and just after wet weather. At these times, also, worms are found frequently under logs and in situations that

are kept moist. Their castings are not always visible on the surface of the soil, since they are sometimes deposited in their burrows. They form rugged masses, sometimes several inches higii, of. finely-divided particles of earth, and it been shown that there is a greater bacterial fauna in the eastings than in the surrounding soil. This is of interest, inasmuch as these bacteria are an important factor in the nitrification of the soil. Another part these Worms play in Nature, from an agricultural stand-point, ia the rendering soluble of certain constituents of the soil that would otherwise bo insoluble, or only dissolve very slowly. The soil particles, with various insoluble or difficultly ’soluble constituents, are passed through the 'body, and are subjected to the various fermentation juices in the body of the worm. This must render some of these more or less insoluble particles soluble and fit for the use ot plants. The extent to which the soil is divided into particles must also have an important bearing on its fertility, because the finer the particles of any given quantity are, the greater will bo their total surface area. This affects both the absorption by the roots of plants* and the retention of -water and soluble materials by the soil. The more finely-divided soil would hold a larger quantity of water when all the free water has been drained away, and "it is also capable of retaining larger supplies of soluble plant food. Worms in some parts have been observed to drag leaves and other decaying matter into their burrows. This, would tend to increase the water-holding power of the soil, and also to increase its fertility.

A few words on the structure of earthworms may not be out of place here. The ■body is cylindrical and ringed—that ie, it ia divided into a number of segments. There is no distinct head portion, but the front end shows a thick lip overhanging the mouth, while the hinder end terminates bluntly. There are no definite appendages, but most of the segments arc provided with little bristles, or sotro, which help the worm in locomotion. These bristles may be felt by' passing the worm through the fingers, and can be readily seen with a lene. In the adult worm the saddle or girdle-like portion surrounding the body snows no segmentation externally, and is situated towards the front end of the body. The mouth ia in the first segment underneath the thick lip, and the vent ie in the -last ring The middle line of the back is distinguished by a clear red line, indicating the dorsal Blood-vessel. If the animal is cut lengthwise along this line so jas to expose the inside, it will be soon that the constrictions between the rings on the outside of the body correspond to partitions, dividing the worm into segments. The organs of the body are clearly visible passing through these partitions on their way from the front to the hinder end of the body. The food canal stands out as a tube filled with earthy material. The accompanying diagram represents the front portion only of a worm that has been cut in this manner, and it will be seen that the food canal in this region is somewhat complicated, although beyond this it is a simple tube. The mouth is surrounded by fleshy lips, and passes on through'the throat to tne crop; this in turn leads on to the gizzard, which is very strong and muscular, and in which most of the * chewing ’ of the earthy material takes place; this is followed by the intestine, a comparatively simple tube which continues to the end of the body. Digestion of the food takes place for the most part in the front portion of the canal. The blood of the earthworm is contained in a definite system of vessels running from the front to the hinder end, both above and below the food canal. At intervals these long vessels are connected to; one ancthor by smaller lateral branches encircling the digestive tube. The blood is coloured red, and is distributed all through the skin by a network of small vessels. There are no special breathing organs in the worm, aeration of the blood being mainly carried on through the skin. The nervous system consists of a small masa of ‘ brain ’ tissue situated at the extreme front end of the body, above the food canal. This so-called brain T» connected to a nerve chain that runs along the length of the body below the digestive tube. It can be distinguished as a thin whitish line near the lower surface of the body. A pair of tiny nerves passes off from this main chain in each segment of the body. “The earthworm has no eyes, but is very sensitive to light, which falls on its front segments. It is also sensitive to vibrations, although possessing no organ of hearing. There are no known organs of taste or smell; but the worm can ‘apparently distinguish red from green cabbage, and exhibits a decided preference for certain foods, such as carrot, celery, onion, and horse-radish.’

“It is of special interest to remember that the group of worms is the lowest and simplest collection ofy forms showing any difference between a front and a hinder end. Although there is ae yet little external sign of cephalisation—that is, of differentiation into a head region,—still, the earthworm has a ‘brain’— ; i.e.. a central nerve mass in this head region. “The distribution of earthworms is of particular importance ae indicating past changes in the contour of the larger land masses of the earth’s surface. Since the earthworm is killed by salt water, it i's evident that it could only migrate, previous to man’s intervention, along land connections The fact that we find allied and very specialised forms in the three southern continents and in certain islands around the Antarctic region undoubtedly points to the former land connection of all these areas.

“ In conclusion, I would like to quote a few words on the distribution of our larger worms from the important monograph mentioned above. Considering the presence of eloscly-allicd forms in South Africa, and in the southern parts of India and Ceylon, as well as in the south of Australia, Professor Spencer says of the earthworms that ‘ the same laws which governed the distribution of other animals must also have governed theirs; and it is just possible that these great earthworms may be the lingering relics of a once widely-spread race of larger earthworms whose representatives at the present day are only found, as occurs with other forms of life, in the southern parts of the large land masses of the earth’s surface. Possibly, careful search will reveal the existence of a large earthworm in the southern parts of South America.’ ” CORRESPONDENCE AND NOTES. Many months ago Mr H. Guthrie-Smith, of Tutira Station, Hawke’s Bay, kindly forwarded a guinea towards purchasing from Mrs Fenton the botanical plates prepared by herself and her late husband. I am sorry that there was no other response to

the appeal, eo I am returning the cheque through the office of the Otago Daily Times and Witness Company. It is a matter for regret that these plates and illustrations are not purchased for the benefit of the dominion.

I am sorry that at present I cannot give any information upon the specimens referred to by the Rev. J. S. Ponder, of Waitahuna. Dr Benham is out of town for a week or two, but when he returns I’ll ask him for his opinion, and write up what I can find out. lam sorry one of the Bpeciments was not sent along in damp earth. , „ , ~ “Taffy Secundus ” (who is he? by the bye; no name came) asks for the identification of a worm. It is an introduced European species known to fishermen in the Old Country as the “ Brandling. It belongs to the species Allolobophora, mq frequents the manure heaps at Home. The dark-coloured alternate bands referred to are limited to the back of all earthworms. It is interesting to examine an earthworm under the microscope. Count the rings, the rows of bristles, etc. Through the courtesy of Mr lannock, I am able to give to-day the essentials of a special article on earthworms written by Janet W. Raff. M.Sc.. and the Government ReseaVch Bursar in the Biological Laboratory, Melbourne, and appearing in the July issue of the Journal of the Department of Agriculture, of Victoria. *llll3 gives the general rule adopted to distinguish Australasian worms from the introduced, and will also supply good notes for a Naturestudy lesson. , , „ “ Fil-gal (Kurow) sends me the following note with specimen enclosed: —“I am enclosing a leaf of a hollyhock which is covered witli a little brown disease. In time the leaf goes in holes and becomes quite brown, and it does not flower properly. Can you tell me a preventive for the disease?’’ I sent the leaf to Mr I. V. Kirk F.L.S., Director of Orchards, etc., and received in return Bulletin No. 12, with the title “Hollyhock Rust.” Elsewhere, if space permits. I am giving the pamphlet, in full for tins d'sease (Puccinia inalvacearum) attacks more than the hollyhocks and causes great damage. As space may not be available this week, I’ll give the spraying mixtures. Before flowering time use the Bordeaux mixture-—2lb copper sulphate (bluestone), 2!b quicklime. 40 gallons of water; if the plant is on the point of flowering use 31b of washing soda instead of the quicklime, because the soda mixture does not stain. “C. M.” (Charlemont st, Ranfurly) sends me an insect frequenting the stagnant pools of Central Otago. “It can crawl on the land as well as swim in the water.” It was pretty well dried up on arrival, but ic- a crustacean of the order Phyllopoda and genus Lepidurns. Hero is the description of the family it belongs to, taken from “ The Royal Natural History ” : “In the family Apcd’doe, containing the genera A pus" and Lepidurus, the anterior end of the body is covered with a carapace [upper shell], projecting from the head over the free segments of the thorax. The hinder border of this carapace is deeply out out, end near its front end there is a pair of contiguous compound eyes. The mouth is bounded in front by a large upper lip and behind by a deeply cleft melastoma fan elevation behind the mouth?], or lower lip. Both pairs of antenna? are short. The jaws consist of a pair of mandibles, and two pairs of maxilla?; these are followed by 11 pairs of thoracic limbs, and there are appendages on the abdomen, sometimes numbering as many as 52 pairs. The last segment of the abdomen hears a pair of long filaments, and sometimes, as in Lepidurue, a distinct caudal plate. Those crustaceans occur in the fresh waters of most countries. They swim on their backs, using their lege as paddles; and the eggs arc capable of surviving long periods of drought when embedded in dried mud.” Perhaps my correspondent, with this description bv her, will examine a fresh specimen nrdcr a pocket microscope. Dr Benham tells mo that for years, together only females are found, so that generations of them are “ fatherless.” Two or throe weeks ago “ AvroLom ” sent me some moths—one just emerging from the pupal skin. These have been identified for me as a night-flying moth, Melanehra eoninosita, but known by other names, particularly Mamestra composita. Hudson's ” New Zealand Moths and Butterflies ” says it is one of our most abundant moths, being found in great profusion throughout the country. As its larva is a destructive grass grub, I am giving some of Hudson’s remarks. The expansion of the wings is about lj>in. The foiewings are pale reddish-brown, darker towards the middle. There are two elongate, pointed white markings touching the tormen [outer margin of the wing] below the middle, and a central white streak, interrupted in the middle by a small semicircular white mark. . . The hind wings aio dark grey. The head and thorax arc reddish-brown, and the abdomen is dark grey. The antenna? are serrate in the male, but single in the female. . . . The larva is bright reddish-brown; the dorsal stripe is broad black; the ventral surface, head, legs, and prolegs are greenish-grey with dark markings; the spiracles are black. This caterpillar varies considerably in the intensity of the light and dark markings. It feeds on grasses in January and September, and is very active, it often occurs in prodigious numbers, and at such times may frequently bo soon travelling at a great rate over bare ground in search of food. Among tbc grass it is hard to detect, as the striped colouring is very protective in that situation. The pupa state is spent in the earth, or under moss or fallen trees. The moth appears from September to April. It is double-brooded. A few of the second brood emerge in tho autumn and hibernate as moths, but the majority pass the winter in the pupa state. Hence wo sometimes meet with specimens on mild evenings in the middle of winter.” The larva is known as the grass caterpillar and army worm

Dear “ Mugister,”—Under separate cover I am forwarding to you a specimen of worm which has, to my mind, a rather peculiar feature. How is it that this particular worm has the rings so marked on its back—i.e., the uppermost part when it is crawling,—while on the underneath part it. is so white and unmarked? I have never noticed such markings on a worm before. Is it because to a different family are seen? If you could find space to explain in your column of the paper, I should be obliged. Taffv Secun'dl's. The Manse, Waitahuna, Nov. 1. Dear “ Magister,”—Can you tell mo anything of a curious annelid I found this afternoon, quite unlike any other I have ever seen in any part of the world? It ie uniformly reddish-brown on the top and

a whitish-neutral tint underneath. Its strangeness consists mainly in its being not round-bodied, but flat, with a fringe like an eel’s fins. It is very sharp-nosed or lance-headed. WHen I saw it first I thought it was a dead worm and its strange fringe was a fungoid growth on the dead body. But when I took it up in my hand to examine it carefully, another one (evidently the female) disengaged itself from the other, revealing the strange belly_ and fringe more decidedly. A few minutes later I dug up a third, in length about 2^in —the longest of the three. Had I had any spirits I would have preserved them and sent them on to the Museum or to you. As it was, I put them back In the ground and watehea their movements as they burrowed into safety.—Yours faithfully, James S. Ponder.