No. 545] ORIGIN OF UNIT CHARACTERS 



255 



earlier and earlier ontogenic stages until they appear to 

 arise prenatally. 



In the titanotheres (Fig. 3) the bony swelling is seen 

 at the junction of the nasals and frontals (black sha- 

 ding), in dolichocephalic skulls it appears chiefly on the 

 nasals, in brachycephalic skulls chiefly on the frontals. 

 Its original low, rounded shape is like that seen in the 

 ontogeny of the horns in cattle. 



2. Horns of Cattle 



The phylogenesis of the horns in titanotheres (Fig. 

 3) is exactly similar to the ontogenesis of the horns in 

 Bovidae (Fig. 2), in which the dermal rudiments first ap- 

 pear soon after the complete formation of the bones of 

 the skull in the unborn young, and the osseous rudiments 

 appear as rounded protuberances in the 8th month. 



In the ontogenesis of horns in cattle three distinct ele- 

 ments are involved: (a) a psychic predisposition to use 

 the horn, (b) a dermal thickening over the bony horn 

 swelling which in ontogeny precedes the swelling, (<?) ap- 

 pearance of the bony swelling itself. 



The ontogenesis is observed to be accompanied by a 

 marked allometric change in the skull which shifts the 

 horn backward from the side of the cranium to the side 

 of the occiput by the obliteration of the parietal bones. 



3. Cranium of Man. 

 A third instance of continuous development is that of 

 the form of the cranium in man (Fig. 1), an allometric 

 evolution, or change of proportion, which is of especial 

 significance because, according to the unanimous testi- 

 mony of anthropologists, 31 head form is the result of 

 very gradual change either in the elongate (dolicho- 

 cephalic) or broadened (brachycephalic) direction. 



"Ripley, Wm. Z., "The Races of Europe, a Sociological Study," 8vo, 

 D. Appleton & Co., 1899, 624 pp. 



