Nos. IAND2.] COTYLASPIS INSIGNIS. 31 



visible and an inner coat of distinctly nucleated cells. Anteriorly the 

 cirrus narrows where it passes into the much enlarged sheath whose 

 wall is slightly muscular, and in addition is lined .with a transition 

 type of cells between the epithelium of the cirrus and the outer cu- 

 ticle, in direct communication with which it stands through com- 

 mon genital passage and the genital opening {cf. Fig. 33). The 

 inner part of the system of passages is narrow, and slightly wound 

 to permit eversion of the organ. In Aspidogastcr there is a very 

 complex system of folds in the cirrus sack which are thought to be 

 employed in everting the cirrus, but nothing like them can be found 

 here. I have not at any time seen any indications of activity in the 

 cirrus, and this, taken in connection with the virtually entire 

 absence of spermatozoa in my material, would encourage the sup- 

 position that the male organs are not in action in July and August. 



iii. The Female Organs. 

 The ovary is always located on the right side directly under the 

 diaphragm and on the level of the center of the ventral sucker 

 (see Fig. 31). It is elliptical and varies in length (in thirteen 

 cases killed under compression and mounted in balsam) from o.i 

 mm. to 0.3 mm. In Aspidogaster the organ is said to measure 

 0.35 mm. in length. Its width ranges from 0.07 mm. to 0.13 mm. 

 It consists of two portions which (Fig. 50), from the point of 

 view of the contained ovarial cells, are very distinct, viz., an 

 anterior part containing very large cells in close relation with the 

 beginning of the oviduct and a deeper posterior portion in which 

 the cells are small and more immature. The ovary is enclosed in 

 a very thin but perfectly distinct wall in which much flattened 

 nuclei can be seen at wide intervals. Stafford considers this layer 

 in Aspidogaster to be a flattened parenchyma. I have seen noth- 

 ing in Cotylaspis to indicate its source. The wall contains some 

 muscle fibers, but they are not very numerous. The cells inside 

 this wall (see Fig. 50) do not form any distinct epithelial layer. 

 As is usual among the trematodes the cells show stages of develop- 

 ment as you go toward the oviduct. I have not traced the stages 

 of ovigenesis completely, but the following observations have been 

 made. There is posteriorly a peripheral layer of cells (Fig. 52) in 

 contact with the outer wall. They are small, have a large nucleus 



