The central and terminal stem of Monodelphia is 

 DiscoiDA. It derives its name from the form of the 

 placenta, which is here discoidal. To this group be- 

 long the Rodents, the Insect Ivor a (including Cheirop- 

 tera)^ the ProsimiiB, the Siniiir, and the central and 

 terminal stem of Hon^inind or Man. 



The two lower branches, Rodentin and Insectivora, 

 include animals which, whilst possessing the essential 

 characters of the group, are inferior in brain develop- 

 ment. They compensate for the extraordinary cer- 

 ebral perfection which characterizes man. 



The Prosimians and Simians together are termed 

 Quadrumana. These, with the Rodents and Insectiv- 

 ora, form a whorl of four lateral branches around the 

 main stem or axis of the group. 



The connection between the Prosimians and the In- 

 sectivora is made by (Taleop'Uhecus^ or the Flying 

 Lemur, an animal held to be an insectivore. On the 

 side towards the Rodents, the Cheiromyini, or the 

 Aj^e-Aye, forms the link of connection. The Mar- 

 mosets, considered as the lowest of the Simians, would 

 seem to be equally well placed if held to be the high- 

 est group of the Prosimians. They are without an 

 opposable thumb, as in one of the Lemurs, — the Aye- 

 Aye. When the face looks forward, as it does in the 

 squirrel-like posture natural to these animals, the base 

 of the brain is almost horizontal to the spinal column, 

 as in the erect human being. The brain case is also 

 relatively very large, although, like the Lemurs, the 

 Marmosets are smootli-brained animals. In the brain 

 there is an excess in quantity combined with inferior 

 quality. The teeth in the Marmosets are thirty-two 



