42 WRIGHT AND MACALLUM. [Vol. I. 



It will be observed that the ootype is here formed of two dis- 

 tinct parts, — one which receives the ducts from the receptacula 

 seminis, and another in which centre the ovarian and uterine 

 tracts of the oviduct, as well as the overflow-tube to the intes- 

 tine. The latter part hardly affords accommodation for much 

 more than the large ovarian ovum, so we gather that the arrange- 

 ment of the food-yolk balls around the &%% takes place in the 

 uterus. 



The slight pressure of a cover-glass is no doubt sufficient to 

 bring about changes, which would perhaps not occur in the nat- 

 ural condition ; but it is very interesting to watch the effect of 

 such pressure upon the receptacula and the vitellogen. Masses 

 of sperm, and especially of yolk, are forced into the first part 

 of the ootype, whence they are discharged by a spasmodic 

 movement into the second. Here they are at once caught in a 

 strong ciliary current, and are rapidly swept into the intestine 

 through what may be termed the overflow-tube. This tube and 

 the ovarian tract of the oviduct occupy approximately the same 

 transverse plane ; the oviduct originating near the dorsal sur- 

 face from the ovary, and running straight toward the ventral 

 surface to its opening in the ootype, from which there like- 

 wise diverges the short, wide overflow-tube to the intestine. 

 We had not observed the discharge of the sexual products into 

 the intestine until we had puzzled a good deal over the end- 

 ing of this overflow-tube, and had satisfied ourselves that its 

 epithelium and the intestinal epithelium became continous at 

 the spot marked * in the diagram. We regard this as an in- 

 teresting confirmation of Ijima's discovery of the true nature of 

 the " internal vas deferens " of -Pplystomum, especially as we were 

 hunting for such an internal connecting tube, and had forgotten 

 his note upon the subject. How such an economical method of 

 disposing of surplus yolk can have been arrived at, whether by 

 the modification of a Laurer's canal or otherwise, we are unable 

 to say. It is probable that further careful researches on other 

 monogenetic and digenetic Trematodes will throw light upon 

 the subject. 



The fact that the surplus material is conducted off by this 

 channel may probably be more easily observed in Sphyranura 

 than in any other monogenetic form, owing to its accessibility to 

 high powers. We have noticed, after prolonged pressure, a 



