1897.] ' On the Affinities of Tarsius : 687 
notes that it is an exceedingly specialized group. I have en- 
deavored to show elsewhere that Tupirulus is probably genetic- 
ally related to the Anoplotheroids, and in this genus the 
canines are fully developed. As far as I can learn it is a gen- 
eral character of the milk dentition that the milk canines are 
weakly developed and much smaller than their permanent 
successors. It appears more likely that the milk dentition 
represents a special adaption during the time that the young 
animal is nourished by the mammary glands of the mother, 
and that the detailed structure of the milk teeth do not accu- 
rately recapitulate the ancestral stages in the evolution of the 
race. However, in regard to the number of the milk teeth, 
that is another question, for we know that in many types which 
in the adult condition the permanent teeth are greatly reduced 
in number, whereas in the milk series the lost teeth appear. 
Among Lemurs Cheiromys is a good example in the reduction 
of the teeth, where the milk dentition is more normal in regard 
to the number of teeth than the permanent dentition, and 
plainly shows that Cheiromys has been derived from some more 
generalized type of Lemur, which had the normal number of 
incisors and premolars. 
In conclusion, the two principal objections in claiming that 
the Lemurs are genetically related to the Apes are, first, in the 
apparently great difference in their placentation, and secondly, 
in the wide divergence in the structure of their dentition. In 
regard to the evolution of the placenta, Dr. Minot remarks 
that our conceptions are still very obscure. The views of 
Balfour which I have lately quoted? as to placental evolution 
in the Primates are clearly untenable, for the reason, as I have 
* See Natural Science, May 1897. 
emphasized before, that in the Apes the allantois is rudi- 
mentary and the placenta arises in the chorion. It is most 
important for the position which I maintain in regard to the 
relations of the Lemurs to the Apes, to notice that in the early 
stages of the development of the placenta in the Anthropoids 
that this organ is completely diffuse and there is no decidua. 
This stage is comparable to the diffuse placentation of the 
Lemurs. On any theory of the evolution of the placenta in 
