ON OCTENOPLANA. 329 
analyse this very complicated longitudinal musculature. The 
musculature! on one side of the stomachal plane is completely 
separated from that on the other side; so that in sections 
parallel with the stomachal plane, passing through the region 
of the sense-organ, no muscles are visible. But at a short 
distance on either side of the median stomachal plane the 
sections in contracted specimens are almost entirely occupied 
by the convoluted bundles of muscles. Again, beyond the 
region of the ctenophoral plates the sections merely show the 
dorsally placed muscular tentacle lying in its sheath (fig. 10). 
6. The Gonads.—By the discovery of the male genital 
organs of Ctenoplana I have brought a welcome additional 
piece of evidence as to the adult character of the organism.” 
The testes are placed at the bases of the two end-lobes of the 
main portion of the gastro-vascular system. Their position is 
indicated by crosses in fig. 1. They thus consist of two pairs 
of organs, paired about the tentacle axis. They may be either 
simple or lobed and subdivided. They may contain practically 
nothing but mature spermatozoa as in fig. 7; or they may 
contain both mature and developing spermatozoa as in fig. 9. 
Finally, they may possess one or several ducts opening to the 
exterior on the dorso-lateral surface of the body below the 
level of the ctenophoral plates. 
The male genital ducts are merely tubular extensions of the 
tunica propria which encloses each testis. 
In the centre of that portion (always the ventral portion) of 
the testis in which the immature sperm-cells (spermatogonia 
and spermatocytes) occur there is usually to be observed a 
cavity surrounded by large clear cells exactly like those which 
line the cavities of the terminal gastric lobes ; and, in fact, I 
have traced this cavity into communication with the gastro- 
vascular system (cf. figs. 5, 6, and 9). 
1 IT do not include the dermal musculature described by Korotueff, about 
which I am at present in the dark. 
2 Unfortunately I can say nothing about the female reproductive organs. 
It seems unlikely that Ctenoplana should be unisexual. More probably it is 
a protandric hermaphrodite. 
