ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
613 
tions may be summarised as follows : — “ It is now established beyond 
doubt that in some at least of the Compound Ascidians the outer layer of 
the bud contributes much less to the structure of the adult blastozooids 
than it does to the adult embryozooids.” This is most conspicuously 
seen in the case of the nervous system, for this is certainly produced 
from the outer layer of the embryo, while it is as certainly produced 
from the inner layer of the bud. Whatever name we give to this inner 
layer, the fact of chief importance remains that the same layer produces 
most of the organs of the zooid, among which are included the digestive 
tract and the nerve-ganglion. The anomalous course of development 
of the bud is due to the fact that the ectoderm is at no time in the life 
of the bud an undifferentiated embryonic layer ; it is from the very 
outset and always a fully formed organ. The inner vesicle of the bud 
is, on the other hand, in the completest sense, an undifferentiated or 
embryonic layer. This is the reason why the inner layer has been made 
to produce structures, and, most important of all, the nervous system, 
which, in the embryo, are produced by the ectoderm. 
As illustrations of the potency of physiological influences to pro- 
foundly change the usual course of development, Mr. Hitter calls 
attention to the budding of other animals ; of these, one of the most 
instructive is the jelly-fish, Bathlcea octojpundata , where the change has 
been in the opposite direction, for here the endoderm takes no part in 
the formation of the bud. The evidence now to hand drawn from the 
blastogenesis strongly tends to the conclusion that the budding of Good- 
siria and Botryllus represents a typo that is independent of that repre- 
sented by Perophora, and would appear to have originated independently 
of it. The budding of Goodsiria greatly strengthens the conclusion, 
justified by adult structure, that the Polystyelidae and Botryllidae are 
very closely related. 
Hibernation of Clavelina lepadiformis.* — MM. A. Giard and 
Caullery find that this Ascidian has become very abundant in Boulogne, 
since the establishment of the new port. The colonies, which are some- 
times as large as one’s fist, disappear entirely during the winter, to 
reappear about the month of June in the succeeding year. They re- 
appear so rapidly that one cannot attribute their growth to the budding 
of oozooids. If towards the end of September or October, or even at the 
equinoctial tides of the succeeding spring, one examines with care the 
place occupied by the disappeared colonies, one finds attached to the 
rocks numerous stolons, which appear here and there like small whitish 
bodies, the whole looking not unlike Bryozoa. This is the form under 
which Clavelina hibernates, reduced to stolonial tubes which are packed 
at certain points with reserve-substances. The colony of Clavelina , 
then, is reconstructed after the winter by budding, which is similar to 
normal budding; reserve-material begins to be accumulated in July, 
and it increases as the activity of sexual reproduction diminishes (August 
and September), and reaches its maximum in the autumn, when the 
whole of the individuals in the colony have disappeared. The process 
of hibernation is comparable to that which the authors have already 
described in the Polyclinidee. 
* 
2 u 
1896 
Comptes Rendus, cxxiii. (1896) pp. 318-20. 
