8 PBOCEEDINGS OF THE NATIONAL MUSEUM vol.70 



middle portion, where the proglottides are very short with bluntly 

 rounded margins ; first distinct segments about 3 mm. back of scolex. 

 The short cirrus opens beside the vagina on a j)apilla in the muscular 

 genital cloaca. The cirrus-pouch varies slightly in size and shape 

 in different sections. In a series of frontal sections it was about 

 0.05 mm. in length and 0.04 in diameter. The folds of the vas 

 deferens lie on the dorsal side of the medullary space between the 

 cirrus-pouch and the median line. The exact number of testes was 

 not indicated in whole mounts, but, as seen in sections, appears to be 

 20 or more. The vagina passes, from its opening beside the cirrus, 

 at first ventrad, then medio-dorsad, enlarging in its course into an 

 elongated seminal receptacle. The ovary, as seen in frontal sec- 

 tions, consists of two lobulate masses symmetrically placed on each 

 side of the median line, where they unite. The vitelline gland is 

 small, lobed, and lies on the median line in front of the ovary and on 

 the ventral side of the medullary space. In a mature but unripe 

 proglottis the vitelline gland was 0.056 mm. in length and 0.056 in 

 breadth; the ovary in the same proglottis measured 0.126 in length 

 and 0.322 in breadth. Rudiments of the uterus were seen leading from 

 the shell gland, and, in proglottides in which ova had begun to appear, 

 the uterus lay on the dorsal side of the ovary ; in mature proglottides 

 it is profoundly lobed. Later the lobed condition gives way to a 

 more or less even outline, when the uterus occupies practically all 

 of the medullary space. Ova with six-hookecl embryos were seen 

 in the ripe proglottides. They have three membranous envelopes, 

 and are about 0.045 mm. in diameter. In sections of adult, but un- 

 ripe, proglottides the inner longitudinal muscle bundles contain from 

 12 to 27, or more, fibers; and the outer from 3 to 7, or more. The 

 circular layer, next within the inner longitudinal layer and sur- 

 rounding the medullary space, is rather distinct. The ventral ex- 

 cretory vessels are much larger than the dorsal. 



This form from the tern has rather more distinct divisions of 

 the strobile into proglottides than is the case with those from the 

 gulls. Indeed there are some suggestions in the anatomy of Fuhr- 

 mann's species T . sarisini, from a tern of New Caledonia. 

 From Larus atricilla: 



The bothria are long-oval, with rather strong muscular border, 

 the capitate appendage is moderately developed. There is a short, 

 unsegmented neck; the first proglottides are much broader than 

 long, and the margins of the strobile are bluntly serrate. The pro- 

 glottides increase rather uniformly in breadth but very slowly in 

 length. The following dimensions are fairly typical: Length 

 52 mm.; maximum breadth 2.5; breadth of proglottis 5 mm. back 



