io6 Transactions of the Royal Canadian Institute, [vol. x. 



The o V a r y is an annular or closed horseshoe-shaped organ, situated 

 ventrally at the posterior end of the middle field of the proglottis (Fig. 

 17). Although in most cases it appears to be completely closed poster- 

 iorly, it is in reality made up of two limbs, — they can be distinguished 

 as such in the very young stages of development — connected 

 anteriorly by an isthmus, on the ventral side of which is situated the oocapt. 

 The limbs themselves are generally enlarged anteriorly, so that, on the 

 whole, they somewhat resemble those of D. latus, which are, however, 

 widely separated behind (Sommer and Landois). The organ is sur- 

 rounded by a very thin wall and is divided by a continuation of the same 

 into a number of irregular, tubular compartments which accommodate 

 the ova. Scattered throughout these partitions and the outer capsule 

 itself, very small, flattened nuclei, from i to 2/i in diameter, are to be 

 seen. This description applies to all of the ovary, excepting that por- 

 tion of the isthmus lying quite near the oocapt. Thus, from the fact that 

 the isthmus — with the contained ova — is solid, it would appear that the 

 views of Sommer and Landois and not those of Leuckart, who considered 

 the isthmus or "bridge" to be a mere duct-like portion of the organ for 

 the passage of the ova, are applicable to this form. 



The largest ova (Fig. 28a), which appear in the ventral part of the 

 isthmus and are thus ready to be passed on for fertilization by the oocapt, 

 vary in longitudinal diameter, since the cytoplasmic outline is somewhat 

 irregularly oval, from 10 to i2/i. The greater part of the comparatively 

 large nucleus, which is about 7/i in diameter, stains much less deeply with 

 Heidenhain's Iron-Haematoxylin than does the surrounding protoplasm; 

 the "nucleolus", on the other hand, comes out extremely dark blue. 

 With Mallory's stain, however, it appears orange, which colour is seen 

 in no other part of the body. Consequently, the nucleolus seems, from 

 its staining powers, to be a definitely functioning body and not a mere 

 aggregation of nucleoplasmic particles. Yet such aggregations, quite 

 as large as the nucleolus itself, are to be seen in other parts of the nucleus; 

 so that from this and the further fact that the outline of the nucleolus is 

 very often irregular, it is a matter of conjecture as to what is the true 

 nature of the body in question. In the cytoplasm of many ova small 

 clear areas, often provided with darkly staining bodies resembling 

 nucleoli, are to be seen (Fig. 28b and c). Some of these may be nuclei 

 forming in the protoplasm de novo (after Young's views), but others 

 so closely resemble small free ova as to lead one to think that they may be 

 abortive ova which have come into intimate contact with the cytoplasm 

 of the normal ova and been subsequently absorbed by them, stages in the 

 process of which absorption are probably represented in Fig. 28c. 



