GERM CELLS OF COELENTERATES 617 



plasm; but the dense, spherical body resembles a nucleolus rather 

 than a nucleus. If the mass represents a nucleus and a nucleolus 

 only, it is of no significance to us, for it must be a portion of a 

 disintegrated cell. If it is a cell with a small homogeneous 

 nucleus it is probably not a germ cell, for such is not the charac- 

 teristic form and proportion of a germ cell. There are some 

 signs of cytolysis evident which leads one to consider this as a 

 degenerating cell. But if we assume that it is a germ cell we 

 find it is as large, almost exactly the same in size, indeed, as one 

 of the young oocytes of the stomach wall. No cells of medusa 

 buds are more than one-quarter the size of this cell which is 

 within the cavity of the canal (compare figure 44 with figures 

 46 to 50), nor are any cells of the medusa buds just like this 

 in appearance. From these facts I incline to the view that this 

 inclusion within the radial canal is a cell, a germ cell if you 

 please, but an abnormal, partly disintegrated cell accidentally 

 in this position. 



There is, then, no evidence at all of a migration of germ cells 

 from the gonad of the main medusa to the budding secondary 

 medusae. This conclusion is based on careful investigation of 

 over fifty individuals examined at every possible path of 

 migration. 



Evidence on the presence of germ cells in the budding zone. 

 Another possible way in which to account for the presence of 

 germ cells in the secondary medusae is to assume that when 

 the primary medusae were first forming, some germ cells were 

 located in the tentacle where they would later be needed to 

 produce the germ cells of the buds. This would be more plausi- 

 ble if all future generations of medusae were present on the 

 main medusa before it left the mother polyp : a grouping of germ 

 cells might occur in each bud rudiment ready to produce the 

 gonads. But as there is an extensive formation of buds from 

 free medusae, buds which begin to develop only after the main 

 medusa is liberated, germ cells should be present, if at all, in the 

 budding zone (i.e., the tentacle bulb) awaiting the opportunity 

 to pass into the buds as they start their development. 



