125 
rosacs ; they also exist between the ectoderm and endoderm of a 
slightly dilated portion of the peduncular blastostyle, immediately 
below the sporosac. I have, however, never seen them here, except 
in a very immature condition ; and it is probable that from this 
situation they subsequently pass into the cavity of the sporosac. 
As the gonophore advances towards maturity, the sporosac is ele- 
vated towards the summit of the capsule, both by its own increase of 
size and by the elongation of its peduncle ; and we now find in the 
female gonophores that the contents of the sporosac become dis- 
charged through the aperture of the gonophore into an external 
oval sac, which at the same time makes its appearance on the sum- 
mit of the capsule ; the now empty and contracted sporosac, with its 
spadix, remaining behind in the interior of the capsule, on the extre- 
mity of its elongated peduncle. 
This extra-capsular sac communicates through the aperture of the 
gonophore, by means of a short tubular neck, with the cavity of the 
sporosac. Its walls are composed of two layers ; the external one 
shows no trace of structure, and looks like a gelatinous investment 
of the sac, but it is probably a delicate membrane, separated from 
the internal by a rather wide interval, which is filled with a liquid ; 
while the internal one, or that which immediately surrounds the mass 
of ova, may be plainly seen to be composed of nucleated cells con- 
nected with one another by a structureless intercellular substance. 
The internal layer would seem to be a simple extension of the endo- 
theque of the sporosac, which now becomes protruded, in the form of 
a hernia, through the aperture of the gonophore. The connections 
of the external layer are more obscure ; but it will probably be found 
that this membrane is an extension of the endotheque of the. sporosac. 
The ova which now occupy the cavity of the extra-capsular sac 
are each found to be enveloped in a special sac, consisting of a very 
delicate structureless membrane, which closely embraces the ovum, 
and is then continued by a narrow elongated neck towards the aper- 
ture of the gonophore, through which it is probably further continued 
into the sporosac, but I was unable to trace it beyond this point. 
The ova in the extra-capsular sac are in a more advanced stage of 
development than in the sporosac ; segmentation has begun, and all 
traces of germinal vesicle and spot have disappeared. After seg- 
mentation has been established, the ovum may be easily broken down 
into distinct cells, with granular contents, but with no evident 
VOL. TV. 
R 
