1887] _ Embryology. 195 
EMBRYOLOGY." 
Notes on Two Forms of Cestoid Embryos.—While engaged 
on the systematic study of the entozoa of*marine fishes in the 
laboratory of the United States Fish Commission, Wood’s Holl, 
Massachusetts, I have made notes and sketches of different stages 
of development of several species of Cestoidea. Without attempt- 
ing at this time to give a detailed account of any one species, I 
wish to present a few notes on two forms which are of frequent 
occurrence. 
To illustrate the first I have chosen a cyst taken from the 
peritoneum of the bluefish (Pomatomus saltatrix), and containing 
an embryo Rhynchobothrium. (Fig. 1.) Cysts like these, either 
of the same or closely related species, are abundant in most of 
the Teleostei, and are also occasionally found in Selachians. In 
the specimen under consideration the length was 12 mm., 
breadth at the widest part6 mm. When removed from its ‘host 
the following points could be made out. The outer covering or 
cyst proper was oblong, larger at one end than the other, and 
tapering uniformly; thin, transparent, and delicate, sag yellow 
granular patches, apparently masses of lymph-cells, on the sur- 
face at the larger end. When the cyst was broken Spell an en- 
docyst TTA Diesing, “ Revis. der Ceph. Ab. Param.,” Intro- 
duction, p. 3) was released. After the escape of the endocyst 
from its enveloping cyst, the latter, retained its shape and was 
not irritable or contractile. It was easily separable into a 
thicker outer and thinner inner layer, both hyaline and formed 
of connective tissue. 
The endocyst when released from its capsular envelope wa 
white and opaque, but became translucent, with a faint bluish 
tinge, when subjected to the action of the compressor and viewed 
by transmitted light. In form, while somewhat variable, it is 
usually club-shaped; much larger at one end than the other; 
the larger end blunt and rounded. The breadth of the larger 
_ end is uniform for about one-third the length of the endocyst, at 
which point there is a sudden constriction, beyond which the 
breadth diminishes gradually to the smaller end. When placed 
in sea-water it continues in a state of activity for hours. There 
is no decided locomotion, but a continuous series of movements, 
consisting of alternate contraction and extension of different 
parts of the sac-like mass and feeble lateral movements of the 
smaller end. In this condition the appearance of the endocyst 
is that of a thick-walled sac, the walls of which are made up of 
granular protoplasm with a thin investing membrane, and filled 
with clear, highly refractile globular masses. When placed 
under the compressor and slight pressure applied, the embryo 
Rhynchobothrium could be seen lying in a loose, irregular coil in 
2 Edited by Dr. JoHN A. RYDER, Philadelphia. 
