94 ILLINOIS BIOLOGICAL MONOGRAPHS [382 



Structure in transections going into the medulla. Just within the inner trans- 

 verse muscles this inner portion of the sac is joined by the uterine duct which 

 with a diameter of 30/i elsewhere is here only 8)u in diameter. Furthermore, in 

 the genital rudiment of the next proglottis ahead there is a distinct demarca- 

 tion between the aggregagion of nuclei that will form the sac and the axial 

 rudiment of the uterine duct. The same separation of sac and duct with the 

 narrowing of the latter just before entering the former is present in the follow- 

 ing segments even where the first eggs are to be seen in the lumen. Thus the 

 eggs must have passed this narrowed region which is a great deal smaller than 

 their diameters. Still farther back where the lumen is about 165^ in diameter 

 there can be seen not only the situation of the sac in the cortex and among the 

 longitudinal m-uscles, projecting as yet only a short distance into the medulla — 

 altho here the bundles of muscles are deflected peripherally — but also the 

 separation of the two parts by a narrow neck only 10^ in diameter. B. cuspido 

 tus shows the same distinct separation oi the uterine duct and uterus-sac in the 

 proglottides where there are already a few eggs in the latter. In Clestobothrium 

 crassiceps conditions were found to be quite the same. When the lumen of the 

 sac attains dimensions of about 60 by 35m and is lined with an epitheUum which 

 takes the counterstain more like a cuticula but shows nuclei on its surface 

 towards the lumen, the uterine duct opens into it with a distinct reduction in 

 diameter. The epithelia of the two are, however, quite similar and continuous, 

 the nuclei being located in a similar mamier in both. Proglottides ahead show 

 that the sac is form.ed by an enlargement of the end of the duct, which takes 

 place first in that region passing thru the cortex quite as in Bothriocephalus. 

 Thus it is seen that the uterus sac of this family is quite different from the 

 functional enlargement of the uterus of the Diphyllobothriidae, with the 

 exception of that of Haplobothrium, since at all stages in its development it is 

 sharply separated from the uterine duct. But as it was not so much this exact 

 separation of the two portions as the constant presence of an " Uterushohle " 

 in this family and its absence in the other, where the " Rosettenf orm " is more 

 commion, that was emphasized by Llihe, and since the structure in Haplo- 

 bothrium is distinctly ptychobothriidian in character, the functional enlarge- 

 ment of the uterus cannot now be considered to be of such systematic impor- 

 tance as was formerly believed. 



PTYCHOBOTHRIINAE Liihe 1899 



Scolex with two surficial sucking grooves, which may be modified by con- 

 siderable growth together of their free edges. Genital openings surficial, those 

 of the cirrus and vagina dorsal, that of the uterus ventral and ahead of the other 

 two. Vas deferens strongly coiled, dorsal. Ovary ventral; shell-gland dorsal. 

 Vitelline follicles usually in two lateral fields in the cortical or medullary 

 parenchyma. Testes com.pletely filling the medulla, mostly marginal to the 

 longitudinal nerves which are well towards the median line. 



Occurrence: Exclusively in fishes. 



Type genus: Bothriocephalus (Rud.) Liihe. 



