2O8 CHAS. W. HARGITT. 



vicissitude is common to many organisms of similar habitat, yet 

 few are so little protected by some skeletal feature as is this 

 wholly naked hydroid. The breeding season at Woods Roll is 

 apparently during June and early July, though colonies may be 

 found in seemingly thriving conditions both earlier and later. 

 Whether Clava like Pcnnana, Eudendrium and others, has its 

 phases of decline and recovery I have not been able to determine 

 from actual observation, though the fact that at recurring inter- 

 vals it appears in the same locations would seem to support this 



view. 



ORIGIN AND GROWTH OF THE EGGS. 



Weismann ('83) was the first to give any direct attention to this 

 problem in Clava. According to him the ova arise in the ento- 

 derm in close relation to the supporting layer, though suggesting 

 that perhaps the most primitive stages may have an ectodermal 

 origin. 



On this point Harm ('02) is quite specific in claiming their 

 origin in the ectoderm, and their later migration into the ento- 

 derm, where in the region of the gonophores they become defi- 

 nitely differentiated and complete their development. This author 

 even goes so far as to suggest that they may be distinguished in 

 the planula as primitive germ cells, --" urkeimzellen " (p. 47, 

 Fig. 48). 



Of course, I am not prepared to discuss the matter so far as it 

 relates to C. sqnaiuata, not having seen this species, but so far as 

 it concerns C. leptostyla I have no hesitation in saying that eggs 

 probably never arise in the ectoderm, but always in the entoderm 

 of the peduncle of the gonophore, or in that of the polyp very 

 near the base of the gonophore. In thousands of sections studied, 

 both by myself and by several of my students, there has been no 

 exception to this statement of fact. Clava, like other hydroids, 

 has its breeding season, during which the germ-cells are ex- 

 tremely abundant, and at other times these cells are either entirely 

 absent or very scarce. Again they do not appear except in direct 

 relation to the forming gonophores or in that immediate region. 

 In fact in Clava leptostyla the morphology of the gonophores and 

 their development as dense, bud-like clusters from a single 

 peduncle to which they are attached by narrow pedicels, make it 



