SURFACE-SWIMMING FAUNA (INVERTEBRATES). 11? 



in the larvae. A Prawn called Palmurus has a 

 larva the body of which becomes extremely ex- 

 panded and flattened, so as to resemble a very 

 thin sheet of glass, the eyes and the limbs at the 

 same time undergoing remarkable modifications. 

 Another larva becomes extraordinarily distended 

 by the absorption of water into its tissues so as 

 to resemble in texture a small Jelly-fish. 



A great deal more might be said about the 

 story of Crustacean larvae, as it is one which 

 is full of interest and wonder, but throughout 

 the whole of it we see, wherever there is a 

 larval history at all, that some one or more of 

 those characteristic features have been evolved, 

 which were previously noted in adult animals as 

 an adaptation to their free-swimming pelagic life. 



In many other groups of marine animals we 

 find the same alternation of a transparent larval 

 life at the surface and an opaque adult life at the 

 bottom. 



The Oysters, Clams and Mussels, the Winkles 

 and other Gastropods, the Worms, the Sponges 

 and many other forms of life that creep among 

 the Sea-weeds and are fixed upon the rocks or 

 burrow in the sand, produce exquisite and delicate 

 transparent little larvae which for a certain length 

 of time at least float and drift about in the light 

 of the sunshine in the surface water. They have, 

 of course, many varieties of form and many pecu- 

 liar organs for locomotion and floatation, so that 

 it is possible for a competent zoologist to tell 

 without much difficulty the group of animals, if 

 not the actual genus and species, to which any 

 particular larva belongs. 



