74 



mSTOKY OF CRUSTACEA. 



Chap. VIII. 



eyes, antennae, and feet, are usually better preserved 

 than in the females; but on the other hand all the 

 appendages of the abdomen have not unfrequently dis- 

 appeared, and sometimes every trace of segmentation. 

 In the females of Entonhcus, which are found in the 

 body-cavity of Crabs and Porcellanw, the eyes, antennae, 

 and buccal organs, the segmentation of the vermiform 



body, and in one spe- 

 cies (fig. 41) the whole 

 of the limbs, disappear 

 almost without leaving 

 a trace ; and Gryiotonis- 

 cus planario'ides would 

 almost be regarded as a 

 Flatworm rather than 

 an Isopod, if its eggs 

 and young did not betray its Crustacean nature. Among 

 the males of these various Bopyridae, that of Entoniscus 

 Forcellanm occupies tlie lowest place ; it is confined all 

 its life to six pairs of feet, which 

 are reduced to shapeless rounded 

 lumps. 



The Amphipoda are distinguish- 

 able from the Isopoda at an early 

 period in the egg by the different 

 position of the embryo, the hinder 

 extremity of which is bent downwards. In all the ani- 



Fig. 42. 



Fig. 43. 



7 Fig. 41. Entoniscus Cancrorum, female, magn. 3 times. 

 ^ Fig. 42. Cryptoniscus iDlanarioides, female, magn. 3 times. 

 ^ Fig. 43. Embryo of a Corophium, magn. 90 diam. 



