618 GEORGE T. HARGITT 



On the premise we have made this must be so, for it has been 

 demonstrated that there is no migration of germ cells from the 

 gonad of the main medusa to its buds. A study of sections of 

 the bell, the canals, and the tentacle bulbs has also made it clear 

 that no germ cells can be recognized in the entoderm of the 

 canals or tentacles, nor in the jelly or sub-umbrellar ectoderm 

 of the bell. It remains to be determined whether there are germ 

 cells present in the ectoderm of the tentacle bulb. It is also 

 desirable to trace the course of development of the medusa 

 buds and see when and where the germ cells first appear. 



Figures 40 and 41 show the characteristic appearance of the 

 cells of the tentacle base, figure 41 showing especially well the 

 large, much vacuolated entoderm cells containing granular inclu- 

 sions, and the more or less vacuolated ectoderm cells. The ento- 

 derm cells are distinctly of the type of those in the gastro- 

 vascular organs. Careful attention was paid to the bases of 

 these cells, but there were no small cells interspersed, no inter- 

 stitial cells, nothing in any way resembling a germ cell. The 

 ectoderm cells likewise are in a single layer, there are no inter- 

 stitial cells here, and neither the cytoplasm nor the nuclei of 

 these cells reminds us of germ cells. It seems that there are 

 no cells in the tentacle bulb which may be recognized as germ 

 cells, indeed none of these cells has the slightest resemblance 

 to germ cells. 



A minute and careful search of all parts of the main medusa 

 has shown that there is no migration of germ cells from this 

 to the developing buds; there are no cells in the canals or the 

 marginal bulbs at the ends of the canals which contain germ 

 cells; the large tentacle bulb from which the medusa buds arise 

 possess no cells either in ectoderm or entoderm which could be 

 called germ cells or mistaken for them; even the budding zone 

 of the bulb shows no indications of germ cells being present. It 

 seems fair to conclude, from all this, that germ cells are not 

 present as such anywhere in the medusa except in the gonads. 

 The gonads which arise in the secondary medusae must then 

 develop quite independently of any germ cells in the main 

 medusae. A study of the development of the medusa buds 

 is, therefore, of importance in determining the origin of these 

 cells. 



