252 



ANIMAL PARASITES AND MESSMATES. 



rhynchus in the alimentary cavity of the sprat, and it 

 is easily distinguished by its peculiar form and its 

 orange colour. 



Fig. 72.— Echinorhynchvs proteus 

 of the Sprat. 



Fig. 73. — Sac with psorosperia ia? , in 

 the Sepia officinalis. 



The 'Asellus aquaticus seems also to serve as the 

 vehicle of the Echinorhynchus angustatus. The hooks of 

 the embryos differ from those of the adults, as the six 

 hooks of the cestodes differ from the crown of the adults. 

 Leuckart has described those of the envelope of the 

 Echinorhynchus proteus and the Echinorhynchus angiis- 

 tatus. The embryo of the Echinorhynchus has only two 

 large hooks on each side, but several smaller ones. The 

 two species mentioned above have on each side five or 

 six hooks placed at right angles with the median line, 

 but they are not all of the same size. 



The animals are allied to the Gordii in their develop- 

 ment. In fact, their development is like that of the 

 echinodermata ; the larva is the Pluteus, in which the true 

 echinorhynchus develops itself, borrowing the skin of the 

 pluteus. According to the experiments made by Schneider, 

 the larvae of cockchafers must be the vehicles of the 



