No. 2.] STRUCTURE OF TWO FISH TAPEWORMS. 345 



ducts can be traced through those proglottids in which no 

 sexual organs are yet developed. One pair lies in the median 

 frontal plane, two pairs are situated below and outwards, — the 

 last being close to the cuticula, — and one pair in the dorsal 

 half of the body, about halfway to the cuticula. Many minute 

 branches are given off from these which open to the outside 

 of the body by pores .005 mm. in diameter, exactly the same as 

 the excretory pores of the scolex. The pores which connect 

 the excretory system with the exterior are simply minute canals 

 through the cuticula, with no special walls. They do not re- 

 semble the very prominent pores found by Riggenbach ('96) in 

 P.fossata and Corallobothriimi lobosiim, being much smaller and 

 without any muscle fibers. They differ also in being much 

 more numerous and entirely irregular in position. 



Throughout the chain of proglottids the minute excretory 

 tubes are connected by these pores in the cuticula with the 

 exterior at various places in each proglottis, being especially 

 numerous near the posterior end of each. 



In the region of sexually immature proglottids a regular 

 arrangement of the longitudinal ducts cannot be so plainly 

 traced. The two which lie in the median frontal plane are 

 the smallest and most regular of all. The others are larger, 

 with many branchings and connections. A transverse section 

 through sexually mature proglottids and those posterior shows 

 a varying number of the sections of the ducts. From larger 

 longitudinal tubes small branches may be traced which curve 

 around the muscle bundles, and either terminate in branches 

 too small to be traced or join some other branch. 



Around the cirrus pouch and vaginal opening near the dorsal 

 surface is a network of rather large ducts arising from longi- 

 tudinal tubes (PI. XVI, Fig. 15). 



There is no connecting vessel at the posterior end of each 

 proglottis, connection, as already stated, being accomplished 

 at various places by irregular branches. This condition resem- 

 bles the description by Kraemer ('92) of the excretory vessels of 

 Cyathocephahis trimcatiis. 



The cuticula of the last few proglottids is fairly honeycombed 

 with excretory pores ; especially is this true of the posterior 



