THE PARASITES.

Auckland Star, Volume LXIX, Issue 300, 20 December 1938, Page 23

THE PARASITES.

HOW THEY DEVELOP. Tho term "parasite" immediately brings to mind such unlovely things as tapeworms, roundworms, lecches and tsimilar organisms, writes a contributor to the "Baltimore Sun." Let us divest ourselves of our prejudice and consider parasites for what they are —remarkable biological adaptations created to meet certain conditions. With the parasites is a vast assemblage of creatures whose hahits border on the parasitic but which have not as yet attained that "low" state. Our common oyster is not a parasite, or even a near-parasite, for it makes its living in its own way. But it lives in close association with a little beast -that is inseparable from the oyster and which is found nowhere else save in a few other shellfish. This little creature is pale and sickly, a washed-out little thing of delicate fawn colour. And its small, under-developed legs are obviously not used very much. These tiny crab creatures liave deserted the normal crab mode of living and have taken up their abode with the oysters. So long have they been associated with oysters that they even have an oyster taste. In tho oyster shells they are safe from all danger and their food is pro-

vided without 'effort 011 tlieir own part. For tlio freely-provided food particles tlio crabs have sacrificed , tlieir colour, their liberty and the strength of their limbs. And the longer these crabs live in oyster shells the more helpless they grow. It is not unreasonable <to assume that in some remote future these erabs may turn from mere companions to fully-developed parasites. It is in this way, scientists believe, that many parasites como into being,' starting as constant companions and then becoming more dependent on the host organism, until the host itself became the food supply.