536 Analytical Notices of Books. 



shell in question, and that the same animal has never been 

 fonnd apart from the shell, excepting perhaps by M. Rafinesque. 



On this latter point, and on the fact observed by Cranch, of the 

 animals having quitted at pleasure the shells in which they were 

 found, he justly remarks that no positive conclusion of their para- 

 sitic nature can be founded ; it being almost certain that this 

 singular faculty must be possessed by the true inhabitant of the 

 uirgonauta, which, on the authority of M. de Blainville, cannot 

 be attached to its shell, on the internal surface of which no mus- 

 cular impression whatever is to be traced. It is to this peculiar 

 circumstance, which is perfectly anomalous among the MoUusca, 

 that the whole of the difficulties with respect to this shell and its 

 inhabitant are to be ascribed. These difficulties are not, we 

 think, satisfactorily cleared up by the present notice ; for although 

 its distinguished author has certainly succeeded in showing an 

 intimate connexion between them, nothing less than a series of 

 carefully conducted observations on numerous living specimens, 

 continued through more than one generation, can finally dispose 

 of the question. 



Our opinion that such a series of observations is still necessary, 

 is not in the least shaken by a note appended to M. de Ferussac's 

 paper, in which it is stated on the authority of an Italian Journal, 

 that the Chevalier Poll had discovered, by means of the micro- 

 scope, the daily developement of the embryo, and the commence- 

 ment of the formation of the shell, in the eggs of the Cephalo- 

 pode, found in the Argonauta Argo. True it is, that if thorough 

 reliance could be placed on this discover)', it would at once be 

 "decisive of the dispute ; if the shell be really formed in the egg, 

 the animal must be the original inhabitant and constructor of it. 

 But the difficulties attendant on very minute microscopical obser- 

 vations are so great and obvious, that we may well be allowed to 

 hesitate, before receiving them with implicit confidence. In this 

 instance, we are bound to view them with peculiar distrust ; for 

 the observation of the Chevalier Poli is contradicted by that of M. 

 Bauer, than whom no one is better versed in the management of 

 the most powerful glasses, and who has stated in the Philo- 

 sophical Transactions for 1817, that what has been taken for 



