550 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
to ripe spermatozoa and the follicular cells. These are the sperma¬ 
togonia, the spermatocytes, and the spermatids. Each kind of cell 
is collected into clusters in different portions of the gonad (pi. 23, 
fig. 9; pi. 25, fig. 26). 
The last generation of spermatogonia (sp’yo.), or primary sperma¬ 
tocytes, is distinguished by having large, oval nuclei and compara¬ 
tively little cytoplasm. The nuclei have a very distinct network 
of chromatin, although the actual number of chromosomes in the 
dividing* cell has not been determined. 
O 
The secondary spermatocytes (sp'go '.) have very sharp nuclei and 
distinct cell membranes, and are naturally considerably smaller than 
the cells from which they arise. They divide to form the sper¬ 
matids, which are distinguished by their small size and the eccentric 
position of the nuclei. Each spermatid is doubtless transformed 
into a spermatozoon, although the details of the process have not 
been observed. 
The follicle cells (foil.) form the lining to the spermary (pi. 25, 
fig. 26) and the duct by which the mature spermatozoa are dis¬ 
charged. They are perfectly similar to those of the ovaries, 
which have been described above. The duct leading from the 
spermary to the surface of the body is formed as far as the base¬ 
ment layer of the integument at an early period, but does not 
penetrate to the surface of the integument until most of the 
spermatogonia have divided up into spermatocytes and these have 
been transformed into spermatozoa. 
In the case of the small spermaries which develop at the time 
when the body of the worm is crowded with developing embryos it 
seems doubtful whether in many instances the spermatozoa are dis¬ 
charged at all. They develop at a time when the tissues of the 
body are taxed to their utmost to furnish nourishment for the 
embryos. Furthermore it is uncertain whether they could be of use 
if they were discharged after the birth of the embryos, for it is not 
known whether any ova mature so late in the season. On the other 
hand the possibility remains that after the discharge of the mature 
embryos the body of the worm decreases very greatly in size, and 
that in this much smaller body the spermaries continue their devel¬ 
opment to such an extent as to again distend the body with sexual 
products, but this time with spermatozoa. This would, perhaps, 
account for the appearance of the pure males of small size at the 
same time that other individuals are carrying embryos. 
