540 J. T. WILSON AND J. P. HILL. 
beyond a period consistent with the general process of dis- 
integration of the dental lamina of which they form parts. 
Worthlessness of Proof from Agreement of Develop- 
ment of p. 83 with that of Supposed Enamel-germs. 
In the passage quoted above from Leche (p. 198) it will be 
found that in discussing the residual laminar downgrowths 
he mentions their agreement with the enamel-germ of p. 3 as 
tending to establish their claim to be regarded as themselves 
rudimentary enamel-organs. 
It is doubtless true that in its evolution p. 3 arises out of 
the residual dental lamina of dp. 3, and that that lamina at an 
early period exhibits the same developmental phase exhibited 
by the residual lamina subsequently developed by the lingual 
sides of the other enamel-organs. But in view of our previous 
contentions the fact of this general agreement can carry no 
weight as a proof of true serial homology. 
Application of the Criterion of “ Contemporaneous- 
ness of Origin.” 
Leche in the next place passes on to apply in this connec- 
tion his favourite criterion of serial homology, viz. that of 
Contemporaneousness of origin of the different An- 
lagen from the dental lamina (cf. p. 528). 
Remarking that the centre of gravity of the whole question 
of the homology of the persisting antemolar teeth of Mar- 
supials lies in that of the relations of dp. 3 and p. 3 to the 
other antemolar teeth, Leche proceeds to apply to this question 
the above-mentioned test. And instead of obtaining a clear 
and unquestioned verdict in his favour on this head he finds 
himself from the first involved in a difficulty, which has to 
be obviated by an important qualification of his doctrine of 
*contemporaneousness.” He finds, in fact, that the Anlage 
of dp. 8 is, after all, not contemporaneous in its first differ- 
entiation with the Anlagen of the other antemolar teeth with 
which he is attempting to demonstrate its serial homology, 
but is really in advance of the latter. The further hypothesis 
