EVOLUTION THE RESULT OF CHEMICAL FORCES. 105 



relics of some of nature's numerous failures in the world-stock- 

 ing enterprise. 



The first departure from the* egg-producing animals, for it is 

 now known that the monotremes are oviparous, were the mar- 

 supials, which bring forth their young in an exceedingly imma- 

 ture state. The mothers take the little embryos, as soon as born, 

 in their mouths and place them on nipples inside of a ventral 

 pouch or receptacle, where they remain until they are large 

 enough to run alone. The young of the kangaroo, which is an 

 animal nearly as large as a cow, when first born are only about 

 an inch long and quite worm-like. They have an embryonic life 

 of only five weeks, and afterwards remain in the pouch about 

 nine months. The embryos in this order of animals never have 

 any connection with the circulatory systems of the parent. The 

 gestation of the marsupials differs but little from that of some 

 few genera of viviparous reptiles. But there is this great ad- 

 vance and difference, that the pouched animals nourish their 

 young to maturity on the milk of the mothers. 



A most singular structural peculiarity is found in the just born 

 embryos of the marsupials. It is the elongation of the larynx, 

 through which air is breathed, across the throat and into the 

 nasal passage, where the end of it, which is like an inverted 

 cone, is grasped by the membrane of that passage, so that res- 

 piration can go on freely and safely while the mother is at the 

 same time forcing her milk down the throat of the helpless little 

 one. In all other mammalia, including the mature of the mar- 

 supials, the larynx opens into, and is on a level with, the bottom 

 of the throat ; but it is protected by what is called the epiglottis, 

 which closes when we swallow and prevents us from choking. 

 Now here is a wonderful adaptive contrivance in a little formless 

 embryo, the only thing that is at all developed in it, and without 

 which it could not live a moment in the place where it is to 

 mature. How will modern evolution account for such a struc- 

 ture as this, which is only of use in a complete and perfected 

 form ? The whole race of developing mammalia would have 

 choked to death long before this absolutely necessary little device 

 had been, by any slight adaptive changes, made effective. 



