494, J. T. WILSON AND J. P. HILL. 
organ of pm [the spaced type is ours]; this, however, 1s 
really not the case; the lamina is morphologically in front of 
that tooth, and only attains a secondary connection with it” 
(2, p. 458). Now, if we disentangle the statement of facts 
from the accompanying explanatory hypothesis, we recognise 
that in the later stage, i.e. when dp? has become thoroughly 
differentiated, a free dental lamina is found by its lingual side 
appearing “as if this lamina was a downgrowth from the inner 
side’ of its enamel-organ. 
But this is precisely the condition we find in Perameles, 
where the appearance of such a laminar “down- 
growth” is most assuredly not due to any process 
of overlapping or disproportionate growth of any 
kind. Nor is there in that form any antecedent enlargement 
of the lamina in front of the dp3 region. We infer from his 
language that Mr. Woodward found some slight difficulty in 
explaining the fact of an actual connection between dp3 
and the lamina by its lingual side, on his theory of a forward 
growth producing overlapping, since he denominates such a 
connection as “secondary.” Now we are firmly convinced 
that no truly secondary connection is ever de- 
veloped between a dental lamina and an enamel- 
organ which has previously been differentiated off 
from the lamina. Itis,a priori, most unlikely that any 
such secondary connection should be established. And we 
believe that, wherever a connecting bridge is present, it will 
be found necessary, and not very difficult, to interpret it as a 
remnant of the original primary connection between enamel- 
organ and parent lamina. We must believe that Mr. Wood- 
ward’s method of explaining away the importance of the con- 
nection he found in his later stage of Petrogale rests upon 
an erroneous interpretation of the facts. We hold that in all 
probability he is wrong in supposing that the part figured in 
the earlier stage in front of dp> is the same as the part found 
in the later stage by the side of that tooth. The latter part is 
simply the free dental lamina of the region of dp® itself, now 
liberated by a more complete differentiation of the enamel- 
