236 



S. YOSIIIDA : 



Sucker oval, o. I mm. by 0.08 mm. on an average. Neck short and 

 very thin. Segments gradually increase in size posteriorly to the few 

 last segments which again grow narrower towards the very end. 

 Widest segment may be 0.4 mm. broad and 006 mm. long Genital 

 pores unilateral. Cirrus long, slender, armed with minute spines. 

 Cirrus pouch a long muscular sac reaching to lateral canals of the 

 aporose side. Three testes arranged in a transverse row dorsal to cirrus 

 pouch. Seminal vesicle dorsal to the inner end of cirrus pouch, con- 

 nected to the latter by short vas deferens. Yolk-gland in median 

 postero-ventral position. Ovary extending transversely, between cirrus 

 pouch and yolk-gland. Vagina running straight inwards from genital 

 cloaca along ventral side of cirrus pouch ; its inner end tortuous, 

 opening into oval, mcdianly situated seminal receptacle. Uterus sac- 

 like, in the last segments occupying all the available space within 

 segment. 



Description. 



External characters. — The cestode may reach a length of J mm. 

 The smallest specimen obtained was only 2 mm. long. The widest 

 segments, which may be 0.3-0.4111(11. broad, ar : (ennd a short distance 

 in front of the posterior end. The narrowest past which is just 

 behind the head, may be 0.07 mm. or less broad. All the segments 

 are constantly broader than long, the maximum length being reached 

 by the posteriormost segment which may be 0.07-0.1 mm. long and 

 0.08-0.25 mm. broad. Segments of the widest parts of the body are 

 0.04-0.06 mm. long. The posterior border of each segment overlaps 

 the anterior border of the next following segment ; consequently, the 

 lateral margins of the worm present a serrated appearance. The 

 serrated condition is most distinct in the contracted state of the worm ; 

 it is frequently scarcely noticeable in the posterior parts (fig. 6), as is 

 also the case with fully extended specimens generally. 



In the live state, the head is very mobile, and is consequently 



