60 THE STRUCTURE OF MAN 



Fig. 41, f)- Thomson, from the study of a large series of 

 skulls, has shown good reason for regarding this as one of the 

 series of Wormian bones which so often occur in this region, 

 and for believing it to arise by dismemberment from either the 

 alisphenoid or parietal.] l 



The nasal bones which, as a rule, remain distinct, sometimes 

 fuse to form one bone. This occurs far more frequently in the 

 lower races (Patagonians and tribes of South Africa) than in the 

 higher ; and it is the more probably an atavism, since this fusion 

 is normal in Apes. In the Chimpanzee it takes place as early as 

 the second year. 



The lachrymals are susceptible to not a few variations, and 

 very rarely an abnormal enlargement of the hamular process 

 causes these bones to appear at the surface of the face, as in 

 many lower Mammals (Gegenbaur). 



Many variations are to be found in the bones of the inner 

 orbital wall. For example, the lachrymal bone may be altogether 

 wanting, or only present in a vestigial form, so that the os planum 

 (lamina papyracea) comes into direct contact with the ascending 

 or nasal process of the upper jaw (premaxilla). In other cases 

 the lachrymal bone may be divided into an upper and a lower 

 portion by a suture, and there are other variations to which it 

 and the development of the hamular process are susceptible ; it 

 may be occasionally replaced by a radially disposed series of 

 small bones. 



A similar division of the os planum of the ethmo-turbinal 

 into several pieces has been observed (Turner, Macalister, Arthur 

 Thomson); but it is questionable if any morphological signi- 

 ficance is to be attached to these variations. 



According to the cousins Sarasin, a lower stage of develop- 

 ment is shown in the skulls of the Veddahs and others, in the 

 downward prolongacion of the nasal portion of the frontal bones 

 into the orbits, which lie very close together and are spacious, 



1 [(Jour. Anat. and Phys., vol. xxiv. p. 356). I have elsewhere pointed out (ibid., 

 vol. xxiv. p. xviii.) that the ossa prseinterparietalia lie within the area normal to the 

 parietals, and that therefore these, at least, among the intercalary elements of the 

 cranium, may be similarly referred to an origin from those bones, by dismemberment, 

 under the expansion of the brain case. The phenomenon appears to me akin to that 

 of the well-known double ossification of the supra-occipital in its most expanded 

 form (ex. Cetacea and some Insectivora), and of the occasional duplication of the 

 lachrymal, and of the os planum, itself already intercalated in the orbital wall in 

 the Primates. (My friend Dr. Forsyth Major has lately shown me that the Lemurs 

 do not differ from the higher Primates in the absence of the latter character, as is 

 generally believed). G. B. H.] 



