MOLLUSCOTBA. 
301 
more thinly, and are about double as long as the others. In this 
condition it leavfes the ovicell; but before doing so the com- 
mencement of the crown of tentacles may be observed. The 
same mode of formation of ova has been observed in Lepralia 
pallasiana (pi. 3. figs. 12-17) ; but here, there being no ovicells, 
the embryos remain in the body- cavity until they are ready to seek 
for a place to attach themselves to in the open sea. Besides the 
smaller cilia, it possesses a transverse circular series of larger 
ones, from which project a cluster of six bristles bent at their 
points ; a portion of these will be from time to time drawn in and 
again shot out : during its movements the embryo would seem 
to employ these sometimes as feelers and sometimes as points 
of attachment. There was also observed at its underside a hofse- 
shoe-shaped elevation, which, compared with the drawings Gosse 
gives of the development of Lepralia coccinea (Devon. Coast, 
p. 218, pi. xiii.), is probably to be regarded as a means of at- 
tachment of the embryo before it leaves the parental body-cavity. 
No spermatozoa have ever been discovered in this form of de- 
velopment, neither before (when they would be expected to 
occur) nor after segmentation ; the production therefore of these 
asexual ova must be regarded in the light of internal buds, com- 
parable to the formation of outward buds ; this form differs, how- 
ever, from that described by Hincks in Bugula and Bicellaria 
(Q. J. M. S. 1861, j). 278). Here also may be mentioned an ab- 
normal formation of ova in Crisia ehiirnea (pi. 4. figs. 1-8), where 
they would appear to arise from an aggregation of free granules 
and vessels, which become surrounded by a membrane. Thus the 
ova arise from a simple differentiation of the Fettkroppar. Some 
such form of development apparently takes place in TubuUpora 
serpens (pi. 4. figs. 9-12), though there is some reason to suppose 
that here it may be owing to a true sexual reproduction. - 
A mode of reproduction very peculiar to the Polyzoa is the 
Formation of Germ Capsules (Groddkapselhildning)i 
In this the mass of Fettkroppar constitutes the basis for the 
origin of the new parts. These germ capsules have been long- 
known by the name of dark bodies’^ (morka kroppar) ; these 
may be seen in Bcrupo cellar ia scruposa (pi. 5. fig.l), in Bugula 
fastigiata (pi. 5. fig. 2), in Eucratea chelata (pi. 5. fig. 3) : here it 
is rcniform, one end light, the other dark, owing to many close 
dark dots; but in Flustra memhranacea (pi. 5. fig. 5) and Le- 
pralia peacliii (pi. 5. fig. 4) they may be well seen. Farre has 
observed two germ capsules in the same cell of Bowerhankia imhri- 
cata. The germ capsules serve the purposes of egg-formation and 
renewal (aterstiillande) of the nutrient canal ; but these purposes 
maybe attained without their existence, as is proved in JEtea an- 
guina. A peculiar form of growth in a new species, JEtea argil- 
