972 J. Us WILSON “AND oJ RP. HUGE. 
molar. ‘To this criticism Kikenthal has omitted to reply 
during the course of his criticism of Leche, embodied in his 
latest publication on this subject—‘ Zur Dentitionenfrage ’ (27). 
And we find him towards the close of this last paper simply 
reiterating the opinion in the course of his remarks in reply to 
Hoffmann. 
We confess that Kiikenthal’s view is still very far from 
being clear to us. When he speaks of the molars as repre- 
senting “ein Verschmelzungsproduct der Anlagen erster Den- 
tition mit dem Material, aus dem sonst die zweite Dentition 
entsteht,” are we to understand that the enamel germs of a 
first dentition are first of all differentiated from certain residual 
“material ” representing enamel-germs of a second dentition, 
and that, having been differentiated from one another, these 
are subsequently fused together? If this be what is meant, 
then certainly the facts of marsupial development give no 
countenance to such anidea. Indeed, the mode of origin, pre- 
servation, and gradual disintegration of the molar residual 
lamina prove that certain “ material”? remains over which is 
not fused or taken up during molar development. 
But if Kikenthal’s words are not to be understood in the 
sense referred to, and if we are to believe that he does not 
conceive of a morphological separation or form-differentia- 
tion ever having been effected between the material of the 
first dentition and the material representing the second (as, 
indeed, his employment of the term material would seem to 
imply), then we can only say that, so far as we can see, his 
view differs but slightly, if at all, from Hoffmann’s idea of 
“ physiological ” fusion. 
The opinions of the last-named author are thus approvingly 
summed up by Leche in a passage which deserves special 
comment :—‘* Will man aber den Begriff der Verschmelzung 
umbedingt beibehalten, so kann man, wie Hoffmann richtig 
bemerkt, und wie auch ich bereits oben (p. 142) hervorge- 
hoben habe, sich vorstellen, dass das Schmelzleistenmaterial, 
welches bei den niederen Wirbelthieren zur Ausbildung einer 
Ganzen Anzahl von Zahnserien verwendet wird, bei den Sauge- 
