SEX DISTINCTIONS 601 



basal pillars which are present in the male. The premaxillaries differ- 

 markedly in shape, those of the male being more closely united and con- 

 verging to a point. The premaxillary-nasal suture in the male is little 

 more than half the length of that of the female. 



A very marked distinction lies in the lacrymal, which is larger and of 

 different outline in the female and has a flush surface, whereas that of 

 the male bears a deep facial depression. The position of the lacrymal 

 duet also varies, as it is single and entirely within the orbit in the female, 

 double and partly external in the male. The facial vacuity formed be- 

 tween the lacrymal, maxillary, and frontal in the female is very much 

 larger and is bounded also in part by the nasal in the male. The frontal 

 foramina are much larger, lie nearer the orbital rim, and their grooves 

 are much more pronounced in the male. 



The position of the infra-orbital foramina is farther forward in the 

 male and the foramina are more complex. The maxillary bone is more 

 deeply molded between the teeth in the male, which, together with the 

 deep lacrymal fossa, is correlated with the greater development of labial 

 muscles to draw the lips back from the tusks. 



The cranium of the male is smoother and the less pronounced temporal 

 ridges fail to meet to form a sagittal crest such as is present in the female. 

 The shape of the occipital region and of the condyles and paroccipital 

 processes also differs. The form of the palate varies, together with its 

 posterior limitation and the outline of the palato-maxillary suture, and 

 there are differences in the position and shape of the basicranial foramina. 



These are characters which are severally used repeatedly by our mam- 

 malian systematists in specific differentiation, and I venture to believe 

 that were these skulls fossil and their relationship unknown, they would 

 be considered as specifically if not subgenerically distinct. 



Ontogenetic Variations 



Humidity reacts most strongly upon coloration of the coat, whether of 

 hair or feathers. It is not clear that it would affect the form or structure, 

 especially of the bones and teeth in an individual, although, of course, 

 there is a racial or evolutionary response to humidity and aridity, both 

 directly and indirectly, through adaptation to a changed vegetative en- 

 vironment. 



Local or geographical color phases or varieties of mammals and birds 

 may be simulated in the individual under artificial conditions and may 

 be, therefore, merely ontogenetic repetition rather than truly racial. 

 Thus, five lions belonging to the grayish buff Felis leo massaica, which 



