AUT. 7 CESTODE PARASITES OF BIRDS LINTON 33 



diameter ; the inner portion of the cirrus-pouch functions as a seminal 

 vesicle. The cirri are slender, slightly tapering, and smooth; maxi- 

 mum length of exserted cirri about 0.11, diameter 0.006. Figure 99 

 is a camera lucida sketch of a specimen mounted in balsam, in which 

 the lateral margin of the strobile is grooved. This may be a contrac- 

 tion feature, although the same peculiarity was noted in more than 

 one strobile. There is an inner seminal vesicle, which is circular in 

 outline as seen in ventral view. It lies on the ventral side of the 

 cirrus-pouch (fig. 97). The three testes are close together near the 

 median line, one poral, the others antiporal. They are relatively 

 large, as compared with the length of a proglottis in the anterior 

 proglottides, but become less conspicuous as the female genitalia 

 develop. The vagina is postero-ventral to the cirrus-pouch. There 

 is a relatively spacious seminal receptacle in front of the ovary at 

 the median line. The ovary was not satisfactorily shown in the 

 mounted material. So far as it could be made out it is small, but 

 little lobed, its two main divisions not quite sj^mmetrical. The 

 vitelline gland, so far as could be determined, is small, compact, 

 and lies behind the ovary. In the posterior proglottides of strobiles 

 measuring 18 mm. in length the uterus occupies the greater part of 

 the medullary space. It appears as a rather compact mass with 

 evenly rounded outlines. The ova, so far as could be seen, in whole 

 mounts, measured about 0.036 in diameter of outer, and 0.018 of inner 

 shell. The ova seen in transverse sections are without shells, and 

 measure 0.015 in diameter. In two strobiles the uterus, in the pos- 

 terior proglottides, is more strongly developed on the aporal than 

 it is on the poral side. This asymmetrical development caused the 

 strobile at this place to become arcuate. Although the segments in 

 one of these strobiles with aporal development of the uterus are 

 shorter, and more crowded together, and the strobile is more deli- 

 cate and fragile than the others, there does not seem to be warrant 

 for regarding it as specifically different from the others. 



Three strobiles, mounted in balsam, and each measuring about 

 18 mm. in length, have the following average dimensions: Breadth 

 of scolex 0.24, diameter of sucker 0.12, length of posterior prog- 

 lottis 0.08, breadth 0.50. 



The only sections made were of ripe proglottides. They show the 

 dorsal and ventral excretory vessel of each marginal pair to be close • 

 together and not differing greatly in size. The genital canals pass 

 on the dorsal side of the excretory vessels. The longitudinal muscles 

 are arranged in two layers, an outer consisting of many small bun- 

 dles, and an inner consisting of eight larger bundles, somewhat sym- 

 metrically placed (fig. 101). The foregoing account is based on 

 material from the herring gull {Larus argentatus) . 

 10582—26 3 



