5G MAMMALIAN DESCENT. [Lect. II. 



After -writing tlie above, I received from Professor Simon H. Gage, 

 B.S., of Cornell University, Ithaca, IST.Y., a most important com- 

 nnmication on the respiration of certain fresh-water Tortoises. The 

 information thus given covers just a page and a half, and yet it is of 

 more value to the biologist than some bidky volumes that one 

 could name. I shall insert it, liodily. Let the facts there disclosed 

 be but fairly ennsidered, and the difficulty of supposing a gradual 

 melting doAvn of the distinctions between the Amphibia and Reptilia 

 will be at an end. 



The lining of the 'jjlianjnx, or ujiper part of the gullet, is the 

 proper normal respiratory organ of any creature possessed of a 

 7iotoc1iord, or p^-irnarij .spinal axis. All the various specialisations 

 that may be found in Ascidians (Sea-squids), AmpMoxi/s (the 

 Lancelet), and in all the Vertehrafa, are of secondary importance to 

 the embryologist. The peculiar structure and functions of the 

 pharynx described by Professor Gage may be due to der/radation 

 or relapsp, but if so, it only proves tJiaf thf aquatic was once 

 the mode of respiration in the stock frum Avhich these Tortoises 

 sprang. 



"I'haryngeal Respiration in the Soft-Shelled Turtle {Aqiidonprtes 

 sjiinift'r). By Simon H. Gage of Ithaca, N.Y. 



"During the last twenty-five years the mechanism (if respiration 

 in the Chelonia has been investigated with considerable thoroughness, 

 both in this country and in Europe ; and at present the Chelonian 

 form of r('Si»iration is considered t(i lie comparal)le with that of the 

 mammal rather than with that of the frog, as formerly supposed. 

 "While, however, the mechanism of respiration has been (][uite fully 

 iuvestigat(Ml, there has been, so far as I am aware, but one who 

 has considered tlie organs of resjiiration in the ditU'rcnt groups of 

 turtles. 



"Professor Agassiz, in Part 11. of the Contrihidions to North 

 American Zoaloijij (p. 284), states that the lung capacity of the 

 soft-shelled turtle is far less in proportion to its body -weight than 

 is that of the land turtles. He also states, in considering this fact, 

 that the skin on tlie ventral side of the body, from its rich network 



