ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
27 
trace the history of development the more do we find the primitive want 
of symmetry, while the larva is like that of normal Gastropods. It 
must not, however, be supposed that Fissurella and the allied forms are 
highly organized Gastropods; while they have become more differen- 
tiated in the symmetry of various organs, they have preserved indubitable 
signs of inferiority. 
It may be concluded that the lower mantle or epipodium is of the 
same nature as the mantle, since the nerves which are supplied to it 
arise from the same parts of the centre as the nerves of the mantle. It 
may also be concluded that the two first ganglia of the asymmetrical 
centre are not limited to the upper part of the nerve-chain which furnished 
the nerves for the mantle and epipodium. If this be so, the groove 
which marks out two distinct and parallel parts in the nervous mass is 
not, as B. Haller supposes, an unimportant groove, but is of high mor- 
phological interest, as it indicates the point of union of the pedal and 
pallial centres. As the nervous system of Fissurella is very like that of 
Parmophorus , the conclusions may be applied to the former which are 
drawn from the latter. 
That there is an ontogenetic and phylogenetic relation between 
Parmophorus , Haliotis , and Fissurella , is shown by the presence in the 
last of two nerve-rings in the mantle, which replace the pallial anasto- 
moses seen in the two first. 
The presence of the vestige of a coiled shell in the young of Parmo- 
phorus and Fissurella show that there is no affinity between these 
molluscs and the Lamellibranchs or the Chitons. 
Nervous System of Cyprsea.* — M. E. L. Bouvier, in consequence of 
some criticisms made by Dr. B. Haller in his recent memoir on Cyprsea 
has re-examined the nervous system in Cypraea arahica. M. Bouvier has 
not been able to find the terminal ganglion in the first branchial nerve 
which has been described by his critic, but he has been able to trace the 
nerve itself and see it innervate the mantle ; the nerve is quite large, 
and can be seen without any dissection. Similar answers are made to 
sundry other criticisms, and some few new details are added. 
Development of a Solenogaster.J— M. G. Pruvot has been able to 
follow out the development of a recently described species of Ponder sia 
— P. banyulensis. The eggs are deposited a few at a time, and are 
covered with a delicate shell. Segmentation is unequal from the first ; 
at the 8-stage there is one large blastomere at the nutrient pole, and 
seven small and equal blastomeres at the formative. Periods of repose 
alternate with periods of division. After twenty -four hours there appears 
a median corona of vibratile cilia, while two ciliated areae appear at the 
cephalic pole and the point of invagination respectively. The embryo 
elongates and becomes divided by two annular constrictions into three 
segments. The cephalic segment is formed of two rows of ciliated cells ; 
some of the cilia become longer than the rest, and one finally becomes 
much larger, and forms the terminal flagellum. The second segment 
or velum is formed of a single layer of cells, which have a single row 
of cilia : these grow and form the ciliated corona, the chief organ of 
* Zool. Anzeig., xiii. (1890) pp. 717-20. f See this Journal, 1890, p. 704. 
% Comptes Rendus, cxi. (1890) pp. 689-92. 
