1894.] Microscopy. 545 
are arranged with their long axes parallel to one another in a little 
cluster near the marginal callosity. The chitinous wall of the capsule 
is thin and transparent, but grows thicker towards the poles. Through 
it the two opaque white eggs or larvæ may be distinctly seen. I have 
never found more than two eggs in a capsule. 
Many of the capsules bear at their outer ends one or more of the 
deep blue thecæ of an infusorium. ‘These were regarded by Gissler as 
pneumatic tubes, but Ryder showed that they were the thecz of 
“ Protozoa of the genus Epistylis or Zoothamnion.” 
Both Ryder and Gissler figure the egg-capsules of Synceelidium 
After describing the capsules of Bdelloura, Ryder: says: “The second 
form, represented in Figs. 5-7, enlarged 16 times, is much smaller, but 
similar in structural features to the preceding. The capsules measure 
about 7s 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 thecæ 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. propinqua, is considerably 
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 B. 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 Limulus-infesting Triclads differ also in their time of. 
breeding. B. candida oviposits during May and early June, when the 
Limuli 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 lat- 
ter part of July and the early part of August, when the gills are de- 
serted by the half-grown young of B. candida for the basal joints of 
the cephalothoracic appendages. As the Limuli have laid their eggs 
and begin to return to deep water by the first days of July, it is neces- 
sary, in order to study Syncelidium and its habits, to collect a num- 
ber of the crabs early in the season and to confine them in a large 
fish-box or similar receptacle. B. propinqua appears to breed‘ at the 
Same time as Syncelidium. 36 
