462 Mr. Morgan's Description of the Anatomxj 



mammary organs of the young animal, which died about two 

 months after it had entirely quitted the pouch, and at an earlier 

 age than any I had previously examined. On opening the 

 pouch after death, I found that not one of the four future teats 

 was to be discovered (Fig. 1.), but that four distinct follicular 

 apertures occupied the situation in which the nipples are 

 afterwards found to protrude : from this circumstance I had 

 no doubt that not only the lower, but the upper teats also, 

 of the kangaroo were originally formed from the eversion of 

 follicular canals, of which the external apertures were thus ex- 

 posed, and that consequently the analogy which I had drawn 

 between the superior teats of this animal and the supernumerary 

 nipples of other quadrupeds, was applicable to their functions 

 only, and not to any similarity in their structure and develop- 

 ment. 



The fact that all the four teats in the kangaroo are formed 

 in precisely the same way, was clearly proved by a dissection 

 of the mammary glands in the young animal before me ; for on 

 tracing the course of the upper follicular openings, I found in 

 them an exact correspondence with that peculiarity of structure 

 which I have already described as existing in the lower mammae 

 previous to the appearance of their nipples (Fig. 2.). At 

 this early period of life, however, it will be seen that the four 

 glands are of nearly the same size, and that they have not yet 

 acquired sufficient magnitude to envelop completely their mem- 

 branous canals. 



It appears then from this dissection and from my former one, 

 that the young of the kangaroo at a very early period of life is 

 devoid of any external mammary organs ; that their first appear- 

 ance is shown in the development of the two superior and appa- 

 rently supernumerary and useless teats ; that subsequently the 

 inferior teats are protruded from their respective glands, and 



that 



