BY T. HARVEY JOHNSTON. 61 



between the middle and edge of the segment. Sometimes they 

 approximate to one surface (the ventral) of the segment, here 

 bordering on the transverse muscle-fibres, a iiai-row s])ace l)eing 

 left between it and the dorsal transverse fibres. It is througli 

 this space that the genital ducts penetrate, while the uterus 

 comes to pass on the other side. 



Tlie excretory trunks lie ventrally to the genital ducts, and 

 arch downwards in passing under them, fn mature proglottids, 

 each vessel becomes very considerably widened, and instead of 

 possessing a sinuous course, such as it has in younger parts of the 

 strobila, forms a wide and low arch. 



At the posterior entl of each segment these main stems ai-e 

 connected by a wide transvere or eommissural vessel, with a 

 lumen of about the same diameter as tliat of the main tubes. 

 On account of the approximation of the latter at the posterioi' 

 end of the segments, the transverse vessels are rather short, in 

 the riper portions of tlie strobila the constrictions lu'twceii the 

 proglottids become so deep, that the vential trunks approach so 

 closely as to make it (Uttieult to distinguish a distinct connuissuial 

 vessel. 



Xervons Si/sfem : — The only parts which could Ix- uiade out 

 were the rather large, longitucHnal nerves. Each was seen in 

 section as a strand lying laterally from the excretory vessel of 

 the corresponding side, just at the edge of the medulla. The 

 genital ducts pass dorsally to it. 



J/«/« (jftui^a/irt .-—The testes occupy a compact, i-ounded zone 

 Iving lietween the main excretory vessel in tlie transvei'se jilanc, 

 and l)etwt'eii the female glands and the transverse excretory 

 vessel longitudinally. Thei-e are about twenty vesicles, of a 

 rounded or elliptical form, with an average size of fi-om O-O.'Ui to 

 0-0-1:7 mm. They are not all in one plane, but are arranged in 

 two or three rows dorso-ventrally. Tlunigh they are generally 

 bounded by the excretory vessels, sonietimes vesicles occui- late- 

 rally from these. In transverse section of a segment, these glands 

 ai-e seen to occupv the middle and uppei' portions of the medulla. 

 In more mature poitions of the strohila. tlii-y are surrounded by 



