86 GERM-CELL CYCLE IN ANIMALS 



garding the germ cells in the following genera is 

 considered below : (1) Eudendrium, (2) Hydractinia, 

 (3) Pennaria, and (4) Clava. 



EUDENDRIUM. Five species of this genus have 

 been investigated. In E. racemosum, according to 

 Weismann (1883), the ova arise in the ectoderm and 

 the male germ cells originate either from entoderm 

 cells or from ectoderm cells that later migrate into the 

 entoderm. Ischikawa (1887) asserts that the germ 

 cells arise in the ectoderm and migrate into the en- 

 toderm, and Hargitt (1904 a) found ova in both 

 the ectoderm and entoderm, but, since those in the 

 entoderm were always the smaller, he concludes that 

 they may have wandered into that layer from the 

 ectoderm, though such a migration was not ob- 

 served. 



In E. capillare Hargitt found ova in the entoderm 

 except in one case where they occurred in the ecto- 

 derm. This author also reports the female germ 

 cells of E. tenue and E. racemosum from the entoderm 

 only. The ova of the EUDENDRID^E when first dis- 

 tinguishable "are slightly larger than the ordinary 

 cells of the surrounding tissue, and differ also in 

 shape, being generally ovoid or spherical and with 

 comparatively conspicuous nuclei. . . . Growth at 

 this period would seem to take place in situ, through 

 the direct nutritive activity of the surrounding tissue 

 cells. ... As growth continues, the ova become 

 more or less amoeboid, migrating toward the gono- 

 phore region, where they seem to aggregate in con- 

 siderable numbers, the presence of which may act as a 



