B72 WILSON. [Vou. IX. 
significance as is advocated in this theory. It is probably an 
adaptive feature acquired within the group of silicious sponges. 
Now whether the gemmule larva has independently acquired 
this adaptation, is open to discussion. I am inclined to believe 
that it exhibits the feature in question, for the same reason 
that it develops germ layers: both features come to it as 
inheritances, the latter from a far distant ancestor, the former 
from a comparatively near one, both features being of actual 
physiological use to the larva. 
To repeat, the conclusion I reach in regard to the marked 
resemblance between the egg larva and gemmule larva of 
silicious sponges is, that it is one not due to independent 
adaptation to similar circumstances, but to inheritance from a 
common source. What I believe I have found is, a bud embryo 
exhibiting ancestral traits. To illustrate by means of an 
imaginary example: suppose the bud of a simple ascidian, 
instead of developing directly into a new ascidian, first devel- 
oped into an ascidian tadpole, with its notochord, nervous 
system, efc., we should then have, I take it, a parallel case to 
the gemmule development of sponges. Only, in the imaginary 
case there could be no doubt of the larval features being inher- 
itances, while in the case at hand I am free to admit that this 
view could be disputed. 
The exhibition of ancestral traits in a bud embryo is perhaps 
a very rare phenomenon. The supposed occurrence of this 
phenomenon in Loxosoma has been shown to be without 
foundation, and Deszo’s claim that it does occur in the devel- 
opment of Tethya buds cannot, in view of the insufficient 
evidence, be admitted. (Moreover, if Deszd’s statement that 
the Tethya bud is derived from a single cell, be a fact, such a 
cell could properly be regarded as an undeveloped germ cell, 
and the “budding” of Tethya would then be a process analo- 
gous to the “sporogonie’”’ discovered by Metschnikoff in 
Cunina proboscidea (38), or to the paedogenesis of the Cecido- 
myia larva, and therefore not a case of asexual reproduction.) 
In fact but a single instance of this phenomenon, as far as I 
know, has been recorded for the animal kingdom, previously 
to the appearance of these observations. The case referred to 
