402 A HISTOEY OF RECENT CEUSTACEA 



In the Cryptoniscidas the first two segments of the 

 peraeon carry very short feet, sometimes degraded, pro- 

 vided at the extremity with a strong claw ; the pleopods 

 are two-branched. The adult female, without becoming 

 unsymmetrical, loses the characteristic shape of an Isopod 

 and all or most of its appendages. 



The Epicaridea in general pass, according to Giard and 

 Bonnier, from the embryo or first stage of their develop- 

 ment to a second or cryptoniscian stage, in which they 

 resemble the males of this family. According to Dr. 

 Pi'aisse the free-swimming Cryptoniscidee have a quite 

 peculiar smell, and the female becomes sexually mature 

 before adopting a parasitic life. Notwithstanding Pro- 

 fessor Kossmann's scepticism regarding the latter state- 

 ment, I believe that it is correct. At all events a minute 

 specimen taken in the tropical Atlantic, retaining all its 

 appendages, and of the shape usual in the ' cryptoniscian 

 stage,' appears to have ovaries crowded with eggs. 



Cryptonisous, Fritz Miiller, 1864. The characters no- 

 ticed hj Fritz Miiller are that the young of Cryptoniscus 

 are, like most other Isopods, hatched with the last pereeo- 

 pods undeveloped, and that the penultimate pair are thin 

 and rod-like, differing much from those which precede them. 



Cryptoniscus planarioides, Fritz Miiller, 1864, was found 

 on Peltogaster purpureus (F. Miiller), together with P/m/ajits 

 resupinatus, on a Pagurid, in Southern Brazil. Fritz 

 Miiller remarks of this species, that, if the eggs and young 

 did not betray the crustacean character, the female would 

 almost rather be taken for a flat-worm (a Planarian) than 

 for an Isopod. 



The Peltogaster, it must be understood, is a strangely 

 metamorphosed Cirripede, which pushes roots into the 

 body of its Pagurid host. Then comes the Cryptoniscus, 

 penetrates the parasite, and draws nourishment to itself 

 through those piratical roots. Strangely it happens next 

 that under this infliction the body of the Cirripede, cheated 

 of its nutriment, dies and falls away, and yet its roots 

 remain and flourish for the benefit of an alien digestive 

 apparatus. Crustaceans of three distinct orders are thus 



