Prof. G. J. AUman on the Anatomy 0/ Actseon. 155 



The general characters upon which the French naturalist main- 

 tains the distinctness of his new order of Gasteropods, are the dis- 

 appearance in whole or in part of the circulatory system, and the 

 transference of the-respiratory function from special organs to the 

 digestive system or common integument, — peculiarities which he 

 asserts draw with them a general degradation of the organism, 

 approximating it to the Acalephse, and thus establishing a group 

 of animals which depart from the type of their class, and are 

 among the Gasteropods what the Entomostraca are among the 

 Crustacea. 



The memoirs of M. de Quatrefages are certainly characterized 

 by great ingenuity and will well repay perusal. They have how-^ 

 over, I fear, thrown themselves open to justly severe criticism, and 

 by advancing statements of great zoological importance upon 

 what must be admitted to be imperfect and too manifestly pre- 

 judiced observations, would, if not corrected, exercise a most in- 

 jurious influence upon a science so strictly inductive as zoology. 

 Of the various animals dissected by M. de Quatrefages in the con- 

 struction of his Phlebenterate group, Actaon is the only one which 

 I have had an opportunity of examining. The result of the ex- 

 amination of this one however is so totally at variance with the 

 anatomy of the same animal as recorded by the French zoologist, 

 that though we can hardly be justified in asserting from this, 

 that his observations on the others are equally erroneous, we must 

 yet surely hesitate before we adopt conclusions of such great im- 

 portance in zoology as those to which M. de Quatrefages has 

 arrived. 



On comparing the description and figures of Actceon, as given 

 by M. de Quatrefages in the memoir to which allusion has just 

 been made, with the structure which my own observation of this 

 animal had revealed to me, I was struck with a discrepancy, for 

 which I must confess I found it difficult to account by reference 

 to any of the ordinary and unavoidable errors to which the obser- 

 vation of these minute animals is necessarily liable. 



Among the most important points in which the observations 

 just recorded difi*er from those of M. de Quatrefages, may be 

 mentioned the detection of a distinct heart and vessels, organs 

 whose existence is denied by the French naturalist, and of a'/o:- 

 teral termination to the intestine, which is described in the fo- 

 reign memoir as opening dorsally and medially. The form and 

 disposition of the gastric ramifications do not at all correspond 

 withM. de Quatrefages' description; the terminal culs-de-sac of this 

 system are arranged very differently from the disposition which 

 he assigns to them, and the ramifications of opposite sides do not 

 communicate. There is certainly no such organ in the posterior 



