Home on Comparative Anatomy. 325 



known, with the consequent process to be gone through, by which 

 the molecule was to become an animated being, no attempt could 

 be made by the most intelligent physiologist, not even by a Harvey 

 or a Hunter, in former times, or a Cuvier in our own, to form the 

 scheme of a general classification upon the principle which is now 

 brought forward. 



The idea of such a scheme originated in finding that the 

 human ovum, and that of quadrupeds, consisted entirely of the 

 molecule. 



In the kangaroo, that this molecule at its origin, was under the 

 same circumstances, but that an addition is made to it before it 

 arrives at the uterus, and in that cavity it is furnished with al- 

 bumen. 



In the opossum of America, the molecule at its origin, has a 

 yelk connected with it in the ovarium, and in the uterus is sup- 

 plied with albumen. 



In the ornithorhyncus the molecule has a yelk connected with 

 it in the ovarium, receives albumen in the uterus, passes through 

 the vagina, and at the cloacus is covered by a calcareous shell 

 and passes out of the body before it is hatchd. 



In the bird the molecule has a yelk connected with it in the 

 ovarium, has a supply of albumen in the oviduct, and having 

 no uterus, a shell is formed in the cloacus and the egg is hatched 

 out of the body. 



" So beautiful a series," as the author calls it, must naturally 

 have made a strong impression upon his mind, bnt whether it will 

 bear him out in forming a new system of the animal kingdom, or 

 what time it will require to bring it to perfection, even if others 

 who follow after him, should adopt it, which in these days of 

 novelty is very problematical, are questions we are not called 

 upon to answer, and wc shall finish this article by an enumeration 

 of the twelve classes, into which, according to this ne stem 



animals are divided. 



SYSTEMA, 



REGNI ANIMALIS. 



N'l'NC TRIAIUM EX OVI MODIFICATIONIBL'S TROPOSITUM. 



Classes. 



1. Eehemctron. Embryo ex ovo in corporc lutco formato evolutus in 



utcro quocum adhsret. 



2. Emmetroa. Embryo ex ovo vel in corpora lutco vcl in vitello formato, 



evolutus in litem a quo solutus. 



3. Ecmetroa. Embryo ex ovo vitello iastructo ct in utcro impreenato 



ucubatione evolutus. 



4. Exoatoa. Embryo ex ovo vitello instructo et in uviducto iiiinrcirnuto, 



ineuliutione evolutus. 



