Toward the period of egg -laying which begins after the winter 

 months, the ovary of Polystoma from the urinary bladder of the frog is in 

 a condition of full readiness for the mass discharge of ripe egg cells. It 

 is almost completely filled with them and only a small intensely-pressed 

 channber near its upper end which is slightly curved is filled with cells in 

 various stages of oogenesis and these are in the "frozen" condition, un- 

 changing for a long period. The envelope of the ovary during this time is 

 thin and membranous. Its separate cells are noticeable only with great 

 difficulty. Just before the very beginning of egg-laying, a process called 

 by us "excision" of the eggs takes place when the egg cells change from 

 the polygonal, as they are during the winter period, into the rounded shape. 

 During the "excision" of eggs not the entire cell is rounded (?, nobis), a 

 part is rejected and completely taken, out as a rule through the genito- 

 intestinal duct into the intestine. The reasons and significance of this re- 

 jection of a part of the cells are completely unclear to us. During the time 

 of the laying the ovary frees itself of a large mass of egg cells, in con- 

 nection with which it even changes its shape to a more extended one. To- 

 ward the end of egg -laying only sex cells which begin to develop strongly 

 remain in the ovary, and they are in different stages of oogenesis. In 

 addition, a certain number of oocytes which were not ejected remain in the 

 ovary after the laying, as a rule in large or smaller quantity. The pro- 

 cess of increased oogenesis, which begins at the end of the laying, continues 

 during the entire summer and terminates in the fall before the departure of 

 the frogs for hibernation. At this time the ovary acquires the same aspect 

 as before laying and remains in this condition until the following reproductive 

 period, that is until the spring of the following year. Parallel to the pro- 

 cess of oogenesis, immediately after the laying an increased process of de- 

 generation of unused oocytes takes place. They gradually fall apart and are 

 seized by the cells of the envelope of the ovary which develop strongly at 

 that time and in which the remnants of the oocytes are digested. The pro- 

 cess of degeneration and seizure of the remnants of the egg cells by the 

 envelope was observed by us among species with long reproductive periods, 

 as for instance Nitzschia sturionis (Abildgaard). During the period of egg- 

 laying the vitellaria, which develop extremely powerfully and occupy the 

 main part of the animal, quickly expend the vitelline cells, and after that 

 they develop intensely again during the summer and toward the winter they are 

 already in the ready state among Polystoma. Among species with an extended 

 period of laying, the expenditure and replenishment of the vitelline cells takes 

 place at the same time. During the period between layings, all the ducts of 

 the female sex system are in the deflated state and empty, whereas during 

 the period of egg -laying they are strongly swollen because they contain some 

 other fluid in addition to the sex products (see further). After copulation the 

 sperm enters into the strongly inflated middle section of the vaginal ducts 

 which among Polystoma functionally replace the receptaculum seminis of 

 other forms (it is interesting to compare it with the blind vaginal ducts of 

 Sphyranura which play the same role; see Jiowever,page 69 ). The expenditure 

 of the sperm and of the vitelline and egg cells in forming the eggs takes p. 85 



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