OF ARTS ANr SCIENCES. 



15 



function of respiration by two methods : first, by nneans of the oxygen 

 of the liquid in its membranes; and second, by bringing a dense net- 

 work of vessels in contact with the air, which passes through the 

 pores of the shell and surrounds the whole formation. In the latter 

 stages of the embryonic development, it is probable that this second 

 method is most efficient, because most direct. 



" From these facts we may conclude that the allantois is, anatomi- 

 cally, an appendix of the Wolffian bodies, and not of the intestinal 

 canal, as has been supposed ; that its subsequent connection with the 

 intestine is produced by an involution of the membranes of this last 

 around the peduncle of the former. But whether this connection is 

 ever a direct and tubular one, I have been unable to determine. 



" Physiologically it is at first the receptacle of the urinary secre- 

 tion of the Wolffian bodies ; but afterwards and ultimately it is a 

 respiratory organ. 



" These conclusions I have arrived at from direct studies, and it 

 will now be interestingto see how they agree with the general facts 

 of the embryonic development of Vertebrata. 



" It is evident that, if the allantois is an appendix of the Wolffian 

 bodies, it would be expected to be met with only in those classes 

 where these bodies are found. In other words, wherever we find an 

 allantois, there ought we to find Wolffian bodies, and vice versa. 



" These relations, I believe, are true. Thus in mammals, birds, 

 and the true reptiles, we find invariably Wolffian bodies and an allan- 

 tois. While in the lower oviparous Vertebrata, as in the Amphibia 

 and fishes, there are neither Wolffian bodies nor an allantois.* 



" Thus it would appear that the views here advanced of the origin 

 and nature of the allantois, are supported by the general embryologi- 

 cal relations of all the classes of Vertebrata." 



Professor Agassiz followed with some remarks. After 

 highly complimenting Dr. Burnett's paper, he stated that cir- 

 cumstances had incidentally led him to investigations upon 



* "A remark is here necessary concerning the reputed Wolffian bodies of Am- 

 phibia. As is well known, these bodies were first described by Mailer more than 

 twenty years since. According to his own description, they differ in almost 

 every respect from the Wolffian bodies of the higher classes. 



"After much examination during this last summer, I have failed to recognize in 

 their structure and general relations the characteristics of the Wolffian bodies, and 

 have therefore ventured to rank the Amphibia, in this respect, with the fishes." 



