576 J. T. WILSON AND J. P.. HILL. 
It may be conceived, of course, that prior to the simple cup- 
shaped enamel-organ, there is a stage like that alleged to exist 
by Rése, in which several mesodermal papille beneath a 
common enamel-germ represent the future tooth. But the 
evidence for the existence of such a condition is as yet so 
extremely meagre and inconclusive that we cannot admit that 
a serious case for it has been made out. 
Schwalbe’s observations in favour of fusion, referred to by 
Kikenthal, cannot be regarded as necessarily possessing any 
great phylogenetic significance. The fusion referred to (16, 
p- 21) of the upper milk incisor with the precociously develop- 
ing crown of the successional tooth need not be taken as 
possessing either more or less morphological importance than, 
e.g., syndactyly in the human subject. Like the latter, the 
condition might even be to some extent hereditary, but its 
interest and importance are probably pathological rather than 
morphological. Were it not for the undeniable importance of 
Kikenthal’s observations on the process of division of the 
cheek-teeth of whales into single conical teeth (19),! and of 
the further statement of the same author that he has been able 
actually to detect a fusion as taking place between molar 
enamel-germs in the case of the walrus (20), we should be 
disposed to regard the fusion theory as a very shadowy hypo- 
thesis indeed. And even with the support alluded to we 
cannot regard its claim to acceptance as at all a strong one. 
There is plenty of room for sceptical criticism. Thus, concerning 
Kiikenthal’s fig. 89 (19) Woodward has remarked (14, p. 447) 
that the condition illustrated and described (19, p. 411) appears 
“rather indicative of the formation of a cusp by outgrowth 
from a simple conical tooth” than of the fusion process 
supposed. 
1 Oshorn has pointed out (84, p. 199) that “even by Kikenthal’s hypo- 
thesis the typical Mesozoic mammal could not furnish as many teeth as are 
found in some of the dolphins;” and he suggests as a likelier explanation 
that “‘as the jaws were elongated the dental fold was carried back and the 
dental caps were multiplied.” 
