382 Miscellaneous. 



bear the name of Peltogaster Prideauxii. It is found exclusively 

 upon Pagurus Prideauxii, but it is rare and always solitary, whilst 

 P. paguri, although much larger, often occurs to the number of two 

 upon the same Pagurus. 



The rearing of the larvse of Crustacea is well known to present 

 great difficulties. It is by capturing with the net and comparing 

 with each other larvse of different ages that in general the curious 

 transformations of these animals have been discovered. Spence 

 Bate, in giving an account of the admirable researches of Fritz 

 Miiller on the nauplian form of Peneus, expresses himself as 

 follows : — " The difficulty of preserving the life of these delicate 

 creatures has not yet been overcome. The newly hatched larva 

 from the commonest and, we might assume, the hardiest crabs has 

 not been preserved beyond the second stage ; and the link between 

 what is termed the larva and the pupa stages of the cirriped has 

 not been demonstrated. It is therefore not to be demanded that 

 Dr. Miiller should succeed beyond the step at which others have 

 stopped." 



The demonstration thus called for by Spence Bate I have been 

 able to obtain for the Cirripedia llhizocephala, and, indeed, by a very 

 simple experimental process. All that is necessary is — (1) not to 

 change the water in which the embryos are living, and (2) to prevent 

 these embryos from coming to dry themselves against the wall of 

 the aquarium which is exposed to the light. This latter inconveni- 

 ence is avoided by raising the level of the liquid from time to time, 

 and by covering the troughs so as to prevent evaporation. 



The numerous broods that I have been able to rear by this pro- 

 cess, not only at Wimereux, but even at Lille, enable me to correct 

 some errors, which it is the more important to indicate because they 

 emanate from very conscientious and experienced observers. In a 

 letter addressed to M. P. van Beneden, and published in the 'Bulletin 

 do l'Academie de Belgique'(2 e serie, tome xiii. 1862), M. Gerbe 

 announces as follows one of the results of his investigations on the 

 animals now under our consideration : — "What has struck me most," 

 he says, " is a constant difference between the embryos or larvae of 

 the same species, a difference which can only be referred to sex. In 

 my opinion the male and female of the Peltogasters when just 

 hatched are already perfectly distinct. The male has that part of 

 him which I shall call abdominal less developed than the female, and 

 the two appendages situated at the posterior extremity are broader 

 and more elongated in the latter than in the former ; but are the 

 internal genital organs appreciable in the two sexes ? This I cannot 

 j'et assert. Nevertheless / should almost venture to regard as an 

 ovary, in the individuals which I believe to be females, an organ 

 situated above the mass which for me represents the liver. This 

 organ, in fact, contains small, spherical, very transparent vesicles, 

 like primitive eggs, and granular like these. If future researches 

 should confirm these appreciations, a corner of the mystery relating 

 to these singular animals may have been lifted from them." 



1. I have shown that, the llhizocephala being hermaphrodites, the 



