THE REPRODUCTIVE SYSTEM 143 



of the numerous offspring. With the reduction of the 

 family, reduction of the mammary series takes place, 

 and animals which produce few offspring at a birth possess 

 few functional mammary glands. The manner of reduc- 

 tion of the mammary series in response to the lessened 

 demands of a diminishing family is in no way haphazard, 

 and, in a general way, it may be said that with a reduced 

 family, those mammary glands are retained which are 

 most convenient for the nursing of the offspring. If, in 

 phylogeny, the family is reduced from ten to two, then 

 instead of ten functional mammary glands persisting as 

 the normal of the species, the number will probably be 

 reduced to correspond to the diminished number of the 

 offspring, and the glands selected for survival will be the 

 pair at which it is most convenient for the mother to 

 suckle the young. This convenience is ruled by the 

 bodily habit and adaptations both of mother and offspring. 

 It is here that the emancipation of the fore-limb enters 

 as an important factor, for the infant is now enabled to 

 grasp the mother, and the mother to grasp the infant. 

 The young of the Lemur grasps tight to the mother's 

 ventral fur, and in this way are carried about by her as 

 she climbs among the branches. The method in which 

 the young hangs on to the mother is curious, for while 

 the mother is engaged in active climbing movements, the 

 infant clings with its head towards the mother's tail. 

 The legs encircle the mother's waist, and the hands grasp 

 the hair of the mother's flanks, the infant's head being 

 pressed against the inguinal region of the mother. The 

 position taken up by the young is doubtless to permit of 

 free arm movements on the part of the mother. Whilst 

 in this position, the infant grasps in its mouth one member 

 of a pair of inguinal nipples which are present in all 

 Lemurs (and some Bats) (see Fig. 54). These inguinal 

 nipples appear to be developed or rather to persist 

 for a very definite reason, and they do not in the majority 

 of cases convey any nourishment to the young, but merely 



