NO. 1123. PROCEEDINGS OF THE NATIONAL MUSEUM. 803 



embryo appears to be held in place by a limiting membrane, which 

 lines the blastocyst and surronnds the embryo. When considerable 

 pressnre is applied, the embryo is forced throngh the walls of the larger 

 end of the blastocyst, with which it no longer retains vital connection. 



The irritability and contractility of the blastocyst continue for 

 several hours after the embryo has been removed. The embryo when 

 removed from the blastocyst was quite active, its length about 24 mm., 

 although capable of considerable variation both by contraction and 

 extension. The bothria are two in number, oblong-elliptical, widely 

 divergent behind, approaching but not uniting in front; emarginate on 

 posterior border and obscurely two lobed (alcoholic specimens show a 

 distinct longitudinal median ridge); edges free, thin, and mobile. 

 Length of bothria, measured while somewhat flattened under com- 

 pressor, 2.23 mm. ; breadth of head, 2.72. Proboscides, four, very long, 

 slender, cylindrical, and armed with recurved hooks of different sizes. 

 The proboscides, in this instance, were not entirely everted, but by 

 counting the series of hooks which were exposed, and allowing for the 

 part which was inverted, which conld be plainly seen through the 

 transparent walls of the proboscis, the result was about one hundred 

 series of hooks arranged in spirals. The spirals are nearly 0.0.5 mm. 

 apart, and the proboscides about 4.8 in length. There are about 

 fifteen longitudinal rows of hooks. These rows do not coincide exactly 

 with the axis, but make about one and a half turns around it from base 

 to apex. Their arrangement is shown in the accompanying sketch 

 (Plate Y, figs. 1-6). 



The proboscis sheaths are long and spiral. A contractile ligament 

 was clearly defined in each and could be traced out into the proboscis, 

 where i-t appeared as a tubular band containing a fluid in which floated 

 a few granules. Toward the end this tubular ligament merged imper- 

 ceptibly in the proboscis, and the fluid interior with granules became 

 the exterior of the proboscis inverted, with, at first, small and scattered 

 rod-like hooks, and, toward the apex of the inverted proboscis, with 

 nornuil hooks attached to the inner i)arietes. 



The front ends of the contractile bulbs lie about 10 mm. back of the 

 apex of the head; length 2.46, and breadth 0.24. The thick walls 

 are composed of diagonal muscular libers which interlace, making 

 angles of about 70 and 110 degrees with each other. These organs act 

 much as the bulb of a syringe. By their contraction the fluid contents 

 is forced into the proboscis sheaths and proboscides. The column of 

 fluid thus forced into the proboscides causes them to unroll like the 

 finger of a glove that has been turned in. The contractile ligament, 

 noticed above, extends the entire length of the proboscis sheath and 

 is attached to the inner parietes of the bulb. By its contraction the 

 proboscis is invaginated from the apex. When the embryo was first 

 liberated, the proboscides were entirely retracted; when, however, 

 pressure was applied, they unrolled. In this condition the proboscides 



