176 BULLETIN OF THE 
small particulars. The nucleus (Fig. 61) is now so small as to be found 
with difficulty among the large opaque yolk granules, the external mem- 
brane is firmer, and the blocks with which it is covered are more promi- 
nent. In this stage the eggs fill the entire body cavity (Fig. 58), being 
roughly arranged in nearly concentric layers. It was from this individ- 
ual that eggs were discharged into the water and later preserved. At 
first sight (Fig. 62) such discharged eggs appear very different from 
those previously described, being armed with a thick covering of long 
conical spines. An examination of the posterior end of this animal, 
which was killed while the eggs were being discharged, showed that the 
eggs which were still in the body and those in the mass outside possessed 
not a trace of these spines, but simply the blocks on the external mem- 
brane, as already described. Further investigation showed that not all 
the eggs which had been laid were already provided with long spines. 
In some cases the spines were very short and thick; indeed, all stages 
were found from this condition up to the one first described. The prob- 
able explanation of this phenomenon is, that the block-like thickenings 
on the membrane of the immature egg are swollen by the sea-water, first 
into shorter, then into longer spines, which at the beginning are proba- 
bly soft and become rigid later. Certainly in alcoholic specimens they 
are rigid. 
In almost every transverse section one finds a delicate membrane 
stretching from the ventral line to the egg mass (Fig. 58). This may 
represent a mesentery, as it is too uniform to be merely accidental. In 
only one case (Fig. 57) was there anything present in the body of the 
female which had the appearance of spermatic elements, but the poor 
histological condition of this specimen prevented an accurate determina- 
tion of the matter. 
The body of the female ends (Fig. 10, and Plate IV. Figs. 56, 57), as 
already mentioned, in a slight bulbous enlargement with a central ter- 
minal opening. The cuticula turns inward for a short distance, as in 
the male, but in the specimens at my command there were no internal 
organs connecting with this opening. The mass of eggs filled the body 
cavity up to the tissue of the terminal bulb. The same question recurs 
here which suggested itself in the case of the male, as to the morphologi- 
cal value of this opening, — whether it is or is not a cloacal orifice ; but 
I have no evidence to present on either side of the question. The bulb 
is made up of elongated cells containing pale nuclei, and passing off at 
right angles to the infolded cuticula. These cells have much the ap- 
pearance of unstriped muscle cells, and seem to be able to affect the 
