place gradually and is regulated on the one hand by the muscular widening 

 of the oviduct which is located at the place of junction with the vitelline duct 

 and which plays the role of a valve in front of the ootype, and on the other 

 hand by means of extrusion of excessive sex products into the intestine 

 through the genito-intestinal canal. Apparently this extrusion should be con- 

 sidered as the basic and only function of the latter. All the sex products^ 

 which in the ootype are surrounded together in determined portions by a 

 shell and in the shape of eggs^are transferred into the uterus from which, 

 after a relatively short time, they are extruded. The function of the uterus 

 is clear; it serves as a place for the preservation of eggs which have not 

 yet been completely formed or hardened and besides, among forms with 

 "rationed" laying, and to that type Polystoma is related, as the place of 

 collection of a determined number of eggs which are set aside at the same 

 time. One must also remark about "shell" glands which forcefully extrude 

 their secretions into the ootype around which they are located during the 

 period of laying. Toward the end of the laying their contents are completely 

 emptied and replenishment takes place gradually during the summer period. 

 The significance of the "shell" glands nevertheless remains unclear. As 

 was already indicated (page 72 ) they consist of two groups and consequently 

 produce two different secretions -- liquids. If one can suppose that one 

 represents fluid which fills the ducts and so to speak "lubricates" the sex 

 products contained therein and first of all the eggs, then what is the function 

 of the second? One can only think that, in spite of the existing views (see 

 Goldschmidt, 1909), this secretion plays a certain role in the formation of 

 egg cells (for more details see page 87 ). 



We should also indicate that among species without the genito- 

 intestinal canal, the unused sex products are also extruded but through the 

 uterus and they are thrown completely outside without any utility for the 

 organism. In very rare cases, especially during the disruption of the 

 activity of the sex system, we observed that unused sex products are ex- 

 truded through the uterus, and among species with the genito-intestinal 

 canals, particularly among Polystoma . Thus, summing up the data con- 

 cerning the function of the sex system in Polystoma , we see that it takes 

 place so to speak in three phases falling into definite periods: preparation 

 for laying, the period of laying itself, and the "post-laying" recuperative 

 period. We see such a distinct periodicity among the large majority of 

 Monogenoidea which have polyannual existence; and among other species one 

 observes the overlapping of one phase with the other and all the processes 

 are more extended in time. 



84 



