544 The American Naturalist. [May, 
MICROSCOPY." 
Marine Planarians.—In a paper now in press (Journ. Morph., 
Vol. IX, No. 2), Dr. Wheeler gives a few notes on methods he em- 
ployed in the study of Planocera inquilina, a Polyclad found in the 
branchial chamber of Sycotypus. 
The Biondi-Ehrlich stain proved to be very useful in making the 
rhabdites conspicuous. 
Owing to the lack of pigment, the nervous system may be traced 
without difficulty, especially in young specimens. It agrees closely 
with Lang’s description and figures of the nervous system of Planocera 
Grafjii. Remarkably clear pictures of the beautiful plexus and its con- 
nection with the brain may be obtained by killing in hot corrosive 
sublimate, staining for 12 hours in Czokor’s alum cochineal, and, after 
dehydrating, mounting in gum sandarac dissolved in absolute alcohol. 
In a second paper, l. c., p. 178, devoted to a Triclad (Synceelidium 
pellucidum) found in the vill-books of Limulus, the method of study- 
ing the nervous system is described thus: 
The great transparency of Syncelidium makes it a very favorable 
object for the study of the nervous system. The brain and main nerve 
trunks may be readily seen in the living animal, but this method is in- 
sufficient for a study of details. It is, however, only necessary to stain 
with alum cochineal, extract as much of the stain as possible with 
water, dehydrate and mount directly from absolute alcohol in gum 
sandarac to obtain a diagrammatically clear picture of all but the very 
finest details of the nervous system. The nerves stand out as white 
lines on a darker background. 
Breeding Habits of the Three Triclads of Limulus.—B. can- 
dida, B. propinqua and S. pellucidum all deposit their egg-capsules on the 
gill-lamellee of their host, Limulus. The first species seems to show no 
preference for a particular region of the gill-leaf, but scatters its egg- 
capsules over the whole surface. B. propinqua selects the basal, or 
proximal region of the leaf, while Syncelidium prefers a small area 
near the edge and just lateral to a small marginal callosity which 
forms a brown line with the callosities of the adjacent leaves when the 
gill-book is closed. . 
The egg-capsule of Syncælidium is about .75 mm. long, of an oblong 
shape and somewhat compressed. It is attached by a slender pedicel, 
-5 mm. in length, in such a way that one of the flattened sides of the 
capsule is applied to the surface of the gill-leaf. Usually the capsules 
‘Ed. by C. O. Whitman, Univ. of Chicago. 
