548 ds T.. “WILSON AND 0, P. HELE. 
in the forms compared, and thus as tending to overthrow that 
homology of the adult marsupial teeth to the Eutherian 
milk dentition which Leche accepts as definitely fixed. 
To this deduction from Leche’s reasoning we have already 
given in our complete adherence, and we are thus after all at 
one with Leche in denying that the so-called “ enamel-germs ” 
are vestigial remains of fully developed successional teeth, 
since we deny that they are “ enamel-germs” at all. 
In further opposition to the interpretation of the residual 
laminar downgrowths as vestigial in character, we may cite the 
fact of the non-occurrence, in any single case, of occasional 
more advanced stages of tooth development, such as might 
legitimately be expected to crop up as the result of atavistic 
tendencies. That such an expectation is not without warrant 
is shown by the fact that in cases where undoubted vestigial 
teeth are found, as in the case of the so-called “ prelacteal ” 
teeth of Leche (our “milk” teeth), these frequently, if not 
generally, exhibit a prematurely advanced and “ abbreviated ” 
developmental condition. 
Denying then, as we do—with Leche—the vestigial cha- 
racter of the supposed rudimentary enamel-germs in Marsupials, 
and—against Leche—their character as successional enamel- 
germs, we have to make the attempt to homologise the mar- 
supial dentition with the typical mammalian upon totally 
different lines. Such an attempt can, we believe, be quite 
satisfactorily carried out, with the help of material in the way 
of facts and observations, of which some of the earliest and 
most significant were contributed by Leche himself. These 
facts and observations concern the existence of representatives 
of an undoubtedly vestigial tooth-series, whose imperfect de- 
velopment precedes the evolution of the persisting adult teeth. 
Concerning the So-called “Prelacteal” Teeth. 
Vestigial representatives of this earliest “ prelacteal”’ tooth 
generation have been described by Leche in Myrmecobius, 
and, as indicated in our introductory sketch, he has interpreted 
the discoveries by Woodward and Rése of similar vestigial 
teeth as demanding an identical explanation. 
