OBJECTIONS AND DIFFICULTIES AND OTHER THEOK1KS 203 



retain an external groove at the line of juncture, and distinct 

 nutrient canals, one for each component (/.//. ox teeth). Superior 

 molars of man, ruminants, horses and other Cumulates, represent the 

 fusion of four simple primitive teeth. 



Thus Ameghino seems to exclude as improbable any secondary 

 division of roots. He also regards such specialized forms as Cetaceans 

 and Edentates as primitive in their teeth. 



P. 20. Probably in all superior molars which are quadrangular, 

 but with three roots, the internal root represents a fusion of two 

 roots. Continuation of this process may result in a single root. Two 

 rooted canines = 2 fused teeth, in normal canines the coalescence has 

 extended to the roots. [Dr. Ameghino does not bring forward any 

 direct evidence to prove the alleged coalescence.] 



P. 29. "We have shown (Filouniln, pp. 88 to 112) that after 

 the fusion which produced the plexodont teeth [quadrangular, quadri- 

 tubercular, quadriradiculate] they soon became either still further com- 

 plicated by the formation of new tubercles, or more simply by the 

 gradual atrophy of the cuspids, tubercles, etc. We have always 

 particularly emphasized these changes, for . . . having examined an 

 enormous number of teeth in almost all groups of mammals, we are 

 convinced of the great facility with which these organs change in form, 

 by the addition or suppression of cuspids, tubercles, enamel folds, creux 

 rentrants valleys, etc., of the crown. 



" We do not share in the opinion that multituberculate molars must 

 be the result of the fusion of as many simple teeth as there are cuspids 

 on their crowns ; the number of fused teeth could only be four or five at 

 most for each tooth. The presence of this kind of molars in the Trias 

 supports the theory of fusion, because if these teeth were the result of 

 gradual complication not only would it be necessary to push back the 

 origin of the mammals to an excessively distant epoch, but also we 

 ought to find in pre-Triassic beds numerous forms intermediate between 

 the conic and the multicuspidate. However, as we do not find any 

 such forms, we are brought to the belief that plexodont teeth are 

 established by a rapid process such as fusion would be." (Translation.) 

 [Another equally rapid process would be the direct modelling up of a 

 cylindrical or conic crown into a basin-shaped crown with cuspidate 

 edges.] 



P. 25. "It is incontestable that the triangular type dominates in 

 the ancient epochs, but this is quite natural since being a modification 

 of the quadrangular type it should of necessity be more abundant: in 

 consequence of the principle formulated elsewhere ' that modified or 

 collateral forms should always be infinitely more numerous than the 

 main stem from which lateral branches spring.'' (Translation.) 



