No. 2.] A NEW MARINE TRICLAD. 181 
sacs are of about the same relative size as in B. candida, but 
nearly twice as numerous; in onespecimen I counted 170 on 
one side of the body and this is probably below rather than 
above the average number for this species. Here, too, the 
sacs extend in between the gut diverticula as compact rows, 
especially in the anterior ramus. 
In sections of Syxce@lidium the wall of each follicle consists 
of a single layer of cuboidal cells with large, round nuclei 
(Fig. 10 ¢sf). Towards the lower inner edge of the sac the 
cells flatten out, and are continued into a thin string-like duct, 
which I have succeeded in tracing for some distance towards 
the vasa deferentia. I have no doubt that Woodworth and 
Chichkoff are correct in regarding these ducts as preformed 
and determinate paths by which the spermatozoa reach the 
vasa deferentia. 
The testicular follicles are normally packed full of spermato- 
zoa in various stages of maturescence. With alum cochineal 
the fully developed male elements take an intense indigo blue 
tint, which contrasts strongly with the purple color of the 
follicular cells and younger spermatozoa. This intense blue is 
very probably an expression of their powerfully cyanophilous 
character, and is of interest in connection with the recent 
researches of Auerbach (9ia, 91») and Watasé ('92). 
The vasa deferentia (Fig. 4 and Fig. 10ovd) lie on either 
side of the pharyngeal chamber, and extend from the region 
of the fourth or fifth diverticulum of the anterior gut-ramus to: 
the keg-shaped penis. In mature specimens they are always 
distended with spermatozoa and sharply marked off from the 
surrounding tissues. Their anterior ends are thread-like, but 
posteriorly they widen out considerably and finally take a 
short and abrupt turn headward, only to turn back again and 
run as very delicate tubules into the penis. These delicate 
ejaculatory ducts widen towards their tips and open by dis- 
crete ‘ostia very near the orifice of the penis. There is, 
therefore, no unpaired ejaculatory duct in Syucelidium as in 
many other Triclads. 
The penis lies in the genital atrium (Fig. 3 gat), which is pro- 
vided with a small opening on the ventral surface of the body. 
