186 WHEELER. [Vou. IX. 
were regarded by Gissler ('82) as pneumatic tubes, but Ryder 
(82>) showed that they were the theca of ‘Protozoa of the 
genus Epzstylis or Zoothamnion.” 
Both Ryder (82a) and Gissler ('g2) figure the egg-capsules 
of Syucelidium. After describing the capsules of Bdelloura, 
Ryder. says : “The second form, represented in Figs. 57, 
enlarged 16 times, is much smaller, but similar in structural 
features to the preceding. The capsules measure about ,, of 
an inch in length and contain usually 2 eggs or embryos. At 
first the ova occupy each one of the ends of the capsule, as 
shown in Fig. 5 ; but after the young worms have developed 
somewhat, they usually lie alongside of each other lengthwise 
of the capsule. They frequently change positions, however, 
at this stage and it sometimes happens that there is but one 
embryo in a capsule.” 
Gissler’s Fig. 2> is evidently the capsule of Syncelidium, as 
shown by its size relatively to the infusorial thecz attached to 
its summit. 
For a description of the egg-capsule of B. candida I would 
refer the reader to the papers of Leidy ('51), v. Graff ('79), Ryder 
(82a) and Gissler (’82). 
What I take to be the egg-capsule of B. propingua, is con- 
siderably smaller than that of the allied B. candida, measuring 
only 1.25 mm. It appears to contain only one ovum, instead 
of 2-7 as in L. candida, but on this point I cannot be positive. 
I am unable to identify this form of capsule with any of those 
described by Ryder (82a). 
The three Lzmzu/us-infesting Triclads differ aka in their 
time of breeding. 4. candida oviposits during May and early 
June, when the Lema return from the deep water to the 
sandy beaches to breed. The passage of the Triclads from 
one crab to another must be favored by the prolonged coitus of 
the latter. Syncelidium oviposits in the latter part of July and 
the early part of August, when the gills are deserted by the 
half-grown young of B. candida for the basal joints of the 
cephalothoracic appendages. As the Lémuli have laid their 
eggs and begin to return to deep water by the first days of 
July, it is necessary in order to study Syncelidium and its 
