CRYPTOTHIRIA. 259 



Sacculina purpurea, which it kills, but whose roots, not- 

 withstanding, continue to grow and frequently attain 

 an extraordinary development. 



" In the genuine Bopj'ridas all the feet are of the same 

 form, while in Entoniscus and Cr-yptoniscus the sixth (or 

 last) pair show a very different structure.'^ The larva 

 of Cryptoniscus has the sixth pair of pereiopoda long, 

 slender, and styliform. That of Entoniscus has the 

 same limbs long and slender, with large and powerful 

 prehensile claws. 



M. Hesse, in his Fourth Memoir on Rare or New 

 Crustacea of the coasts of France, *' Ann. des Sci. Nat. 

 1864, ser. v. vol. ii. p. 281," described and figured the 

 female of Pcltogaster tau, which he found on Paguri, 

 together with its monoculoid-cirriped-like embryo. More 

 recently (in his Tenth Memoir, 76ic?. vol. vi. p. 321, 1866) 

 he gives an elaborate account of P.paguri, in which he 

 describes an animal, of which he had only taken a single 

 specimen on a Pagurus, and which he considers, without 

 sufficient proof, as the male, together with the female, 

 and the young animal in its earliest stage of develop- 

 ment. The earliest form of the larva he describes as 

 resembling that of the Entomostracous Crustacea, and 

 states that, as in all of the suctorial crustaceans, the 

 larva has three pairs of appendages. He also describes 

 it as having latei-al processes on each side of the anterior 

 margin of the head, and that these processes are im- 

 mature antennas, thus proving its relationship with the 

 Cirripedes, and leading us to infer that the parent animal 

 which he figures as the female is bisexual, and that his 

 supposed male has no connection with the female, but 

 must be considered as that of a Bopyroid crustacean, 

 possibly of a Cryptothiria in an advanced stage of 



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