10 C. S. MINOT ON DISTOMUM 



species also. These observations seem to me sufficient to justify the conclusion that this 

 canal exists in all Trematods, while it is evidently the same as the vagina in Cestods. No 

 corresponding tube has yet been observed in any of the Pharyngocoela. 



AH the female organs thus far described are lined by a delicate membrane, which is 

 lightly colored by carmine ; it appears structureless, and I have not noticed any epithelium 

 or muscular coats connected with it. 



I have to add that the uterus does not always begin with just such curves as are repre- 

 sented in Fig. 6, Ut. Upon leaving this part of the body it runs backward, enlarges, and 

 after a very long and irregular course it passes forward, diminishes its diameter, and curves 

 downward on the left of the penis, beside which it finally opens. Around its terminal 

 portion there are numerous cells, probably glandular, having large nuclei, very much like 

 those seen in the penis. 



The shell gland and the beginning of the uterus are . surrounded by numerous pear- 

 shaped cells, containing a nucleus in the rounded end, while the narrow neck, which is sup- 

 posed to act as a duct, is directed towards the uterus. These cells have been found in a 

 great many Trematods and Cestods, and are supposed to secrete the matter that forms the 

 egg shells ; if this be the case, they will probably be found in some form in Planarians, etc. 

 They are so much alike in Trematods and Cestods that they afford an additional argument 

 for the union of the two orders. 



The egg food stocks, as may be seen for example in fig. 4, do not form two solid glands 

 but are broken up into a number of more or less spherical divisions (fig. 10), from which! 

 run out short ducts ; all those of one side finally collect together in one common duct, 

 which runs obliquely backward, meeting its fellow from the other side directly over the 

 shell gland. I cannot say in what manner they .finally open into the shell gland. They 

 can be seen in fig. 1 as two dark lines, one crossing the ovary, the other passing just in 

 front of the left testicle. 



All the cells in the food-stocks appear to be fully developed, and I find none still 

 undergoing change into food cells ; this agrees with the large number of eggs in the uterus 

 indicating that all my specimens had been sexually mature for some time. The food-cells, 

 fig. 16, are large and spherical, with a pale nucleus placed centrally, but nearly concealed 

 by the great number of large refringent granules in the protoplasm, giving the yolk cells 

 their brownish coloring. The cells seem to be more or less distinctly separated from one 

 another, each having a special membrane, but with no visible intercellular cement. This 

 structure of the food-cells is common to all Vaginifers, at the time the cells are ready 

 to break loose and pass to the shell gland. 



The eggs in the upper part of the uterus are elongate spheroids in fig. 15, A, and 

 the food-cells already reduced in size, can still be distinctly seen. Further down the ute- 

 rus the eggs gradually become concavo-convex, as appears most distinctly in optical sec- 

 tion, fig. 15, B, the shell growing much thicker and more resistant. Freshly laid eggs 

 still present the same appearance. 



The central nervous system appears as a transverse fibrous band overlying the hind end 

 of the oral sucker (fig. 2), and enlarged at each side where the ganglionic cells mostly he. 

 They are indistinct in all my preparations. I could not follow any nerves from the band. 

 In position and appearance it is exactly like the central nervous system in other Trematods. 



! 



