900 J- Stafford, 



half ahead of tlie other, and they are long and somewliat lobed on 

 their outer sides. In the other thi^ee species they are small, rounded, 

 or elliptical, compact bodies, one some way in front of the other. 

 The anterior ends of the festes narrow into vasa deferentia, thin 

 ducts which run forwards and unite at the posterior end of the 

 penis sack. This is a much broader bnt still tolerably narrow and 

 pretty unifoi-m, tubulär organ, stretching from the proximity of the 

 ventral siicker to the external genital pore. Its posterior part 

 contains the vesirula seminalis, and its anterior part the ductus 

 ejaculatorius, while between these and the penis sack are prostate 

 glands. Both the anterior end of the Uterus, or vagina, and of the 

 penis open, together, into a short sinus, communicating with the 

 exterior by the genital pore. All of these latter organs are too 

 difflcult to examiue, or are too much alike in the several species, 

 to be of use in distinguishing them. 



The vitellaria consist of two longitudinal, latero-dorsal rows 

 of about ten bunches of follicles, lying above the intestinal caeca, 

 and connected by a duct on each side, which from its middle gives 

 oif a transverse brauch — the two latter uniting to form a vitelline 

 reservoir, which opens into the oviduct as alread}^ mentioned. A 

 very good way to see the ducts, follicles, and in fact many other 

 Organs, is to allow the worm to remain in water for a time, when 

 it will lay the great mass of its eggs, thereby becoming transparent, 

 and may be studied alive, or preserved and mounted. The vitellaria 

 are too much alike, or are too variable, to be depended upon and 

 can only be taken into account with other organs. 



The Egg was the first sure guide in distinguishing those 

 species that are most alike. It is approximately of the same size 

 in Nos. 1 and 2 ; in Nos. 3 and 5, it is of equal size but larger 

 than in the first pair; in No. 4, it is larger still. The thick, hard 

 Shell does not shrink (it may double longitudinally) under the 

 influence of re-agents, so that the eggs of preserved or mounted 

 animals or of sections may be compared with those of living ones. 

 In making measurements it is well to select eggs of similar age and 

 of normal size and structure. There are always.imperfectly formed, 

 irregulär, small ones. A convenient way is to take those first 

 extruded from the genital pore of each worm. 



The Development, Metamorphosis, Intermediate Host & c. will, 

 I am satisfied, throw light on the difference of species but they are 

 not yet sufficiently known. 



