TEACHING A SNAIL

Evening Star, Issue 21571, 17 November 1933, Page 7

TEACHING A SNAIL

REMARKABLE EXfEMMENT ’: . ■ . i . Gan a snail learn? • Does it profit . - by experience? Can it be made to change Us . ways? Is it adaptable? Or-does ifwbrlc,. by instinct alone? According .to the on a spring morning the/snail is. to. be found on the top twig of the thombush. ,«■ But in the maximum Tight! and; heat,of_ a warm’day it; hides-in the shadow of a moist v cove 'of ferns or 'other leafy plants. To' thawhorticulturist the snail is a nuisance,'for hr® night it cuts wide holes in the leaves of carefully tended' plants • and 'scurries .away • with vh.e dawn to hide in some dark,' dank recess. - ; , Such conduct gives the impression that a snail is a crafty, designing individual---/., actually destructive by ' night, but quietly t hiding out- by day.' It has no designs,however, since" it is almost /altogether' creature of;. stereotyped, instinctive .be- ~ baviour. It seeks the darkness because.'of - what has been called a negative heiiqtropism—an instinctive turning- away* from the light. But, with a r little training, the ' land snail has been made to. change its ways to a certain extent. This'-wis doE*' at the University of Denver'by-Mary‘Piqk-/ ncy Mitchell; and it was the negative, helto* tropism which made the training possible,. • Miss Mitchell- was curious to know just, how far down the animal scale /weymly , go, and' still find learning of a; sort. For. the subject of her experiment-she /selected 1 a land snail, Bumina decollata Linuaei, which is notorious for its. destructives**' to valuable plants. Since - she • remembered ' that a snail runs away from the light, cinstructed a maze.of glass,.and this.mase was simple enough, for it was in. the form T of a T. The stem of the T was eighteen centimetres long (a - centimetre , w, .39=7 of an inch) and the arms, taken -together, fifteen centimetres. .Both .stem, «md; arms, ', were 3.5 .centimetres wide and . 2.7 centimetres deep. ~ • . , ,■ ■ ■■ :. , •, The class T. was cemented to a window glass; on top. arid it restedon .amovable, sheet of glass. At the end of ,th«loft arm were two wire loops which, act«L as electrodes, and at. the end of the ngW arm was a dark box. Suspended foot of the maze was a‘7s-wstt lamp.'w^.,. The snail was.to learn to:go up t5e,A.,... starting at the foot, -and'toi turn.vto-the. vicht where the arms qomed the sUm, qn« . continue until >it reachedof the .dark box • at Hhc . end;; of > the r^htarm. This was called a i .trial. If, of turning to. The right. The. snail ijOTedto tlie left.and continued to that end, or the maze it was punished by coming in con--tact with the electrodes. ; , ...

HOW THE TRAINING SUCCEEDED. ■■ * The procedure' ■was- -to ...take ■ from ». bucket- filled with. mpuldy place it at the .foot of the “«c----the shell -with a drop otwatei, and tuilT, on the .lamp. .The moment dbe-wad;!«£•• tvuded its one foot and-horned,*“* %*.. Mitchell started a stop-watch, for then thelearner would start on the trip up the, stem of the T. the electric drive, and -the glass sides, and top of the maie allowed S £™ U l* B continue acting until the daik box on the. right was reached. The training, process continued months -daily- with the exception of Satui- . days and Sundays. Often fee was mom than one trial a day. And the_aatu learned; for, as the training proceeded. lhe time for trial was cut down _ from • seconds to 205 seconds, errors droppedpubentirely, and the path, which was exceedfngly. tortuous and indirect atJr*, toward the end as siraightforwaid a-patM nc a snail > could make ii* ■ .... After the last trial the snail . was avowed ’ then eS Uen itS out U< 'and memberea; it is sufficient to state , tbak this the 103rd, trial was made, in AB3fe&V ffi no errors and a fairly direct ‘path«-