1887] | Embryology. 199 
refractile masses much smaller than those in the blastocyst, and 
enclosed in an investing membrane about 0.005 mm. thick. 
The posterior end is terminated by a papillary, button-like pro- 
cess, which is retractile and covered with a dense coat of minute, 
straight, hair-like bristles. (Fig. 5.) 
Another form of cyst I will notice briefly and illustrate by an 
embryo Tetrarhynchobothrium, taken from the surface of the 
liver of the cero (Cybium regale). (Fig. 7.) This cyst is long 
and slender, about 10.5 mm. in length and 1.5 mm. in breadth, 
yellowish, opaque, but broken in places so as to show the out- 
line of the blastocyst. 
The blastocyst, which is set free, when the walls of the cyst 
are ruptured, is long and slender, with a neck-like constriction 
at one end. (Fig. 8.) The head part. thus set off is very 
changeable in form, expanding, contracting, moving up and 
down and from side to side, and revolving with a rotary move- 
ment on the constricted neck. The longer part or body of the 
When compressed the embryo is discovered lying in a coil in 
the head of the blastocyst. (Fig. 8.) The parenchyma of the 
head part is now seen to be much coarser than that of the body 
part, the coarseness being due to the presence of numbers of 
large, oval, refractile fluid spaces. The parenchyma of the body 
is dense and finely granular, with smaller refractile masses than 
those in the head part. When the head part of the blastocyst 
is braken open the embryo is released, but instead of separatin 
from the blastocyst, as in the case of the embryo Rhynchoboth- 
rium, the blastocyst remains attached to the body of the scolex ` 
much like the Cystocercus of Tenia. The method of release, 
however, is quite different from that of the Cystocercus of most 
Tæniæ. Instead of unfolding like the finger of a glove, the neck 
of the scolex first emerges in the form of a loop. (Fig. 9.) 
While in this position the head lies close beside the base of th 
neck in the vicinity of the contractile bulbs. The head is re- 
leased by a simple straightening of the neck, which at its base, 
a short distance back of the contractile bulbs, remains attached 
to the head part of the blastocyst. (Fig. 11.) In this speci- 
men, after the head of the scolex was released, the anterior part 
or head of the blastocyst continued for some time working 
backwards and forwards on the neck of the scolex like a mova- 
ble barrel on a stationary piston. (Fig. 10.) Considerable press- 
re was applied for the purpose of making the scolex separate 
entirely from the blastocyst, but without causing it to break loose. 
When pressed out as far as it would go, it could be seen that 
there was an unbroken continuity between the scolex and blasto- 
