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 

 I'oughly 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 eg'g 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 uustriped muscle cells, and seem to be able to affect the 



