CHAPTER III 



THE MEMBERS OF THE MAMMALIAN ORDER. PRIMATES 



In the foregoing chapter the relative positions of the various 

 Orders of the Class Mammalia were briefly reviewed from the 

 standpoint of evolution. If it be assumed that the typical or 

 representative mammal has during the period of its evolution 

 passed through vertebrate stages corresponding respectively to 

 those of the Fish, Amphibian, and Reptile, it seems intelligible 

 that in some mammals a greater number of ancestral characters 

 occur than in others. Such mammals as possess a greater 

 number of such reminiscent characters should be regarded as 

 primitive, while others should be described as less primitive, or 

 more highly evolved. 



From this standpoint there is much evidence for assigning 

 the lowest place among the Mammalia to the Order Monotremata 

 composing the Sub-class Prototheria. In series above these, and 

 consequently less primitive in their degree of evolution, are the 

 Metatheria, among which the Order Polyprotodontia is more 

 primitive than the Diprotodontia. Above the Metatheria 1 come 

 the Eutheria, consisting as has been already remarked of some 

 nine Orders. 



Allusion has been made already (p. 32) to the difficulties met 

 with in grouping the various Eutherian Orders. The accompanying 



1 It is not surprising to find that while the Prototheria and Metatheria may thus 

 be regarded as primitive or slightly evolved, there are not lacking those who would 

 regard some of their features as the result of extreme specialisation and even 

 degeneracy. For the brain, at least, the statements made in the text appear to hold 

 good (cf. Elliot Smith, " Origin of the Corpus Callosum," Linn. Trans, vn, Ser. 2), 

 and to the brain-evidence much weight must admittedly be attached. 



