AND THOSE OF CERTAIN OTHER MAMMALIA. 99 



Falten des Eitheils so verwachsen sind dass sie bei der Geburt vom Uterus abgeris- 

 sen werden.' 'The vascular cells or folds or otherwise shaped organs of the uterus 

 from the connexion of the mother and foetus are so interblended with the vascular 

 villi and folds of the foetal parts of the membrane, that in parturition they are torn 

 away from the uterus.' 



There are, however, it must be confessed, but few propositions 

 which can be made of all unguiculate, or of all deciduate mammalia 

 beyond those which the two names connote. These, however, by 

 themselves are sufficient to justify us in retaining the binary 

 division of Professor Weber, coinciding as it does so nearly with 

 the class founded by Linnaeus on the peculiarities of a system so far 

 removed from the reproductive as is the tegumentary. And to 

 them we may add the defenceless condition in which the young 

 of nearly all deciduate mammalia, except the elephant (and 

 Hyrax ?), are brought into the world, and the general, though not 

 universal co-existence in them of multifid livers and multifid 

 lungs with simple stomachs. The value of the placentary system 

 of classification is much better seen when we come to the sub- 

 divisions of Weber's great class, when we see that of each of the 

 well-established orders, Simiadae, Insectivora, Rodentia, and Car- 

 nivora, a well-established and distinct aggregation of placental 

 characters can be predicated. Of the Chiroptera I do not speak, 

 as I have only been able to examine a single example from this 

 order, and that but for a short time and at a comparatively early 

 period of development. Of the placentae of the four other orders 

 we may say, as perhaps of the entire sets of characters belonging to 

 each of the orders themselves, that those of the Carnivora are more 

 distinctly marked off from each and all of the other three than is 

 any one of the other three from any other of the three ; and of 

 these three the Insectivora possess, on the whole, a nearer affinity 

 to the Simiadae than do the Rodents. In each case the characters 

 are those of the placenta at or near full time. 



In the Simiadae we find the ultimate ramifications of the um- 

 bilical vessels confined to the placenta ; and in it the foetal capil- 

 laries are probably not merely apposed to similar maternal vessels, 

 but plunged within a maternal sinus-system. The presence in 

 them of structures known as decidua reflexa and decidua vera show 

 that all the aeration and all the nourishment which the foetus 

 receives comes from the single or double placenta, and not at all 

 from the extra-placental uterine mucous membrane. The de- 



H % 



