VOL. LXXXV.] PHILOSOPHICAL, TRANSACTIONS. 543 



they cover a greater length of the nipple, giving the mouth a better hold ; the 

 upper surface of the tongue, as that organ grows, is concave, adapting it to the 

 nipple which lies on it. The growth of the foetus is distinctly seen in the an- 

 nexed drawings. 



From the peculiarities in the structure of the female organs of the kanguroo, 

 it is evident they must, in their mode of generation, materially differ from other 

 quadrupeds. The semen of the male passes in a circuitous way through the 

 lateral canals to the cavity of the uterus, and from the structure of the parts, 

 can neither enter the fallopian tubes, nor readily return to the vagina. The 

 embryo, in its passage from the ovarium along the fallopian tube, will be enve- 

 loped in the gelly formed in the oval glandular enlargement of that canal, and 

 in this state deposited in the uterus, where it will come in contact with the 

 semen of the male. 



This differs from other quadrupeds, but exactly coincides with all those ani- 

 mals whose fcetuses are detached ; the semen being retained in the lower part of 

 the oviduct, where it comes in contact with the egg when completely formed. 

 In other quadrupeds the influence of the semen is ascertained to have reached 

 the fallopian tube, by well attested cases of the foetus never arriving at the 

 uterus. In this animal such an effect is rendered difficult, and not very pro- 

 bable; it is therefore more natural to suppose the impregnation takes place in 

 the same way as in the detached fcetuses of other animals. 



This mode of nourishing the young resembles, in some respects, what takes 

 place in the dog-fish, whose egg is deposited in the oviduct, and hatched there. 

 The yolk of the egg in the bird being conveyed into the belly at the time of its 

 being hatched, made me desirous to see if any of the gelatinous substance of 

 the uterus was conveyed into the belly of the young kanguroo, but I could not 

 on dissection find any such appearance; and as it is to be immediately attached 

 to the nipple, there is no apparent necessity for such a provision. The egg of 

 the turtle and dog-fish, which live in water, is similar to the contents of the 

 uterus in the kanguroo in being composed of one substance only, which renders 

 it probable that in birds it is made up of 2 substances, on account of the young 

 being longer unable to procure its own food. If we consider the varieties which 

 occur in the formation of different animals as so many parts of the same system, 

 the mode of generation just described will be found, in this chain of gradations 

 of nature, to form a link between animals whose young are nourished by means 

 of a connection with the uterus, and those that are nourished independent of it. 



Explanation of the Jigures. — PI. 6", fig. 4, is a posterior view of the uterus, and its appendages, 

 the rectum being being removed. The parts are represented of half the natural size, a, the cli- 

 toris, inclosed in its praeputium ; bb, the ducts of Cooper's glands j cc, the internal surface of the 

 vagina ; d, the meatus urinarius ; ee, the canals leading from the vagina to the uterus : ff, two 

 natural constrictions in the canals j gg, the canals terminating in the uterus ; hh, the uterus, seea 



