THE CRUSTACEA 123 



Some, on the other hand, are far from beautiful. One 

 species (Bopyrus squillarum) has all but lost every vestige of 

 legs, and every other organ, except the digestive and re- 

 productive parts. It has also lost all symmetry, and is 

 contorted to suit the position it has elected to occupy for 

 life. This is parasitic on the gills of the prawn, just beneath 

 the side of the carapace, which it causes to bulge out in a 

 wartlike process about the size of a pea. This description 

 applies to the female. 



The male is symmetrical, and can swim at sea, although 

 he is usually found with his consort, but the male is easily 

 overlooked, as he is almost microscopic in size. 



The little " Gribble " (Limnoria lignorum) is about a 

 quarter of an inch long, broad for its length, and mottled 

 yellow and black. It bores into timber, and is the ally of 

 Chelura terebrans, already mentioned. 



Some small species are frequently found in the osculse 

 of sponges ; and in the little hollow sacklike Sycandra 

 compressa are often found the pretty Anceus maxillaris, 

 the male of which has a very large head and a formidable 

 pair of serrated jaws, looking like some dentist's uncanny 

 instrument. The female is of a bright azure blue. 



Some figures of the chief types in these orders are given 

 in Fig. 48. 



Somewhere between the crustaceans just dealt with and 

 the higher division the " stalk-eyed " there is a curious 

 form, named Nebalia. It has stalked eyes like the following, 

 but the body is segmented all along, instead of having the 

 first segments fused together into a carapace, but then 

 again it has a carapace in the way of an enveloping shield, 

 which covers the anterior segments. It has characters 

 belonging to the Entomosttaca, and to the two divisions of 

 the Malacostraca. In fact it appears to be a survival of 

 an ancient type, which had the rudiments of the characters 

 which now appear in strong differentiation in the different 



