The Ovogenesis of Hydra. 308 



description applies to the formation of the ovary in H. viridis: in 

 both other sorts the procedure is similar but several ovaries appear 

 at once, crowding each other and rendering' observation of the 

 histological details difücult." 



"I have ascribed the increase of interstitial cells that form the 

 ovary entirely to cell division and certainly this is is largely the 

 case. These interstitial cells seem to be exceptionally infrequent in 

 the neighborhood of the growing organ, however, so that it is very 

 likely that migration also adds to the enlargement of the ovary. 

 That this is the case I can not affirm for I have not seen it and 

 do not know if the interstitial cells are capable of migration." 



"When the ovary has reached the above stage, a cell which 

 usually lies at the center of the organ begins to grow rapidly: this 

 is the is the %^g. At first it agrees in its characters completely 

 with the other cells of the ovary and is, therefore, unrecognizable. 

 It is now first distinguished because its longitudinal diameter is 

 greater than the transverse and because its margin is marked by 

 short pointed processes. In older eggs these processes become larger 

 and one often finds, in the midst of the plasma, a circular to eliptical 

 space filled with a clear liquid: whether the formation of this 

 vacuole is constant at this stage is not known; it is, at any rate, 

 of short duration. Now the %^g cell begins to assume the butterfly 

 shape; the nucleus increases in size and the nucleolus also. There 

 now appear in the body of the ç^gg irregular, rounded bodies of 

 varying size; they are shiny and look much like the fat droplets 

 that are abundant in the plasma, but they are rather of the nature 

 of the white of ç^g^ which appears in eggs of both vertebrates and 

 invertebrates and which His calls protagon, Kühne vitellin. In the 

 hydra egg they disappear again promptlj^ and only the tiny granules 

 of the plasma remain. Still farther the &gg grows, broadening, the 

 , wings' becoming more apparent, their borders irregular," 



"In H. viridis the chlorophyll bodies now begin to form; there 

 appear small bodies in the ^gg, sometimes few, at times many, some 

 green, some such as appear in the endoderm cells of H. grisea and 

 H. aurantica colorless or pale yellow. They appear at the center 

 of the egg quite as often as at the periphery: they always begin 

 as colorless bodies and the coloring is added when the body has 

 attained its usual size. In these respects they agree with the 

 method of formation of the chloroplasts in Vaucheria and Bryopsis 

 (Hoffmeistee)." 



