NO. 1123. PROCEEDINGS OF THE NATIONAL MUSEUM. 817 



form of a loop. While in this position the head lies close beside the 

 base of the neck in the vicinity of the contractile bulbs. The head is 

 released 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. In this specimen, after the head of the 

 scolex was released, the anterior part or head of the blastocyst con- 

 tinned for some time working- backward and forward on the neck of 

 the scolex like a movable barrel on a stationary i)iston. Considerable 

 pressure 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 the blastocyst. The 

 posterior tapering end of the scolex, however, was clothed with straight, 

 fine, hair-like bristles like those noticed in an embrj^o Bhyncliohotlirium. 



The bothria are four in number, in opposite, lateral pairs, spreading 

 from the front of the head. They are quite mobile, sometimes with the 

 sucking disks turned forward, sometimes backward, and with a retract- 

 ile proboscis, armed with long, slender, slightly recurved hooks, 

 belonging to each bothrium. The proboscides were everted but a short 

 distance, but they were apparently fully developed. Tlie proboscis 

 sheaths are spiral and the contractile bulbs slender. A reticulated 

 system of vessels in the margins of the bothria and sinuous longi- 

 tudinal vessels behind the contractile bulbs and near the edges of the 

 blastocyst were made out in the living specimen. 



In a specimen which was lightly stained with carmine and placed in 

 glycerine, the scolex and body part of the blastocyst are red, while the 

 globular head-like part of the blastocyst is golden yellow, the staining 

 fluid only showing faintly in some longitudinal central vessels. This 

 same part in unstained specimens in alcohol is yellowish and more 

 opaque than the body, which is white with a faint bluish tinge. 



The development of this form at this period differs from that of 

 BJiyncJiohothrium, in that the blastocyst is retained as a part of the 

 scolex after the latter is released. I have repeatedly tried the experi- 

 ment of opening blastocysts of these two types, with the results in 

 every case the same. In the one case the embrj-o does not seem to 

 have any permanent connection with the blastocyst when the walls of 

 the latter are broken; in the other, the embryo can not be removed 

 from the blastocyst without breaking a connecting bond. The finding 

 of a specimen ^ in the intestine of a sting ray ( Trygon centrura) proves 

 that the blastocyst maintains its connection with the embryo for some 

 time and through many vicissitudes. It is highly probable that it 

 thus forms a part of the adult strobile, or at least remains attached as 

 a nutritive vessel until absorbed by the growing strobile. 



Following are brief exceri)ts from memoranda made on some of the 



' United States Fish Commission Eeport, 1897, p. 861, pi. xv, fig. 2. 

 Proc. N. M. vol. xix 52 



