ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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and cnidophorous sacs, nerves in the neighbourhood might be diverted 
from their original positions, and become drawn up into the cerata. 
The authors point out that it is impossible to regard all these cerata 
as pallial outgrowths supplied by the pleural ganglia, and that it is 
possible that they may have been epipodial in origin, although some are 
now connected with pleural nerves. 
Development of Proneomenia.* — M. G. Pruvot has made a study of 
the ova of Proneomenia aglaophenise, which are of some size, and sur- 
rounded by a supple and transparent shell. Segmentation is slightly 
unequal, and ends with the formation of a blastosphere with a small 
segmentation-cavity, which is by invagination converted into a gastrula 
with a large blastopore. The larva escapes covered with fine cilia. 
Like that of Dendrosia it divides into three segments ; the cilia form 
a crown at the base of the median segment, and soon unite to form a 
long flagellum at the depressed apex of the cephalic segment. At the end 
of the sixth day the young has the form of a small, very contractile 
worm, completely covered with large discoid imbricated spicules, ex- 
cept along the median ventral line which is ciliated. These spicules 
only form a provisional investment, which is replaced later by long 
acicular spicules imbedded in a thick cuticle. 
The primary endoblast does not correspond to the definite endoderm, 
but, by a special process, gives rise to all the tissues of the trunk of 
the adult. Its cells divide actively, and give rise to a superior endo- 
dermic mass which rests on a vault formed by a single layer of cells. 
These last increase and give rise to a layer folded in such a way as 
to form three diverticula, the lateral of which are mesenchymatous. 
By the closing of the orifices of the lateral diverticula the invagi- 
nated vault is formed a second time into an uninterrupted cellular 
layer, but one which is exclusively ectodermic, and one which is alto- 
gether employed in the formation of the epidermis of the body. The 
periphery of the proctodaeal orifice forms a caudal button which is 
the origin of the whole of the trunk of the future Neomenian. As 
this elongates it carries into its interior the lower portion of the endo- 
dermic mass. 
The adult Proneomenia has no distinct head, although there are 
during development distinct signs of the formation of a true head, the 
appearance of which the author describes. 
The facts detailed in the present communication and the similar 
phenomena seen as Dendrosia banyulensis , indicate that the development 
of the Neomenian differs considerably from that of the Mollusca. On 
the other hand the formation of the layers has a close resemblance to 
that of the Hirudinea, and may to a certain extent be compared with 
the Pilidium-stage of a Nemertean. 
Arthropoda. 
a. Insecta. 
Larva of Lagoa.j — Prof. A. S. Packard has some notes on this 
Bombycine caterpillar, which has seven pairs of abdominal legs. This 
* Comptes Rendus, cxiv. (1892) pp. 1211-4. 
f Zool. Anzeig., xv. (1892) pp. 229-34 (2 figs.). 
