PORIFERA, CQELENTERATA, VERTEBRATA 87 
stimulus from which results the formation of the 
gonophore” (Hargitt, 1904 a, pp. 261-262). 
Hypractinia has been investigated by van 
Beneden (1874), Weismann (1883), Bunting (1894), 
and Smallwood (1909). Weismann considered the 
ectoderm of the blastostyle to be the probable place 
of origin of the germ cells in this genus. Bunting 
(1894) was unable to trace the ova to this layer, 
although she found them to be quite abundant in 
the entoderm of the blastostyle, even before the gono- 
phore appeared. According to this author the ova 
apparently arise in the entoderm of the blasto- 
style, and ‘“‘reach maturity on the outside wall of 
the spadix, lying between the endoderm and the 
inner layer of the bell nucleus. The spermatozoa 
arise from the inner layer of the bell nucleus; we 
see that they are, therefore, ectodermal in origin” 
(p. 228). 
These results are not confirmed by the researches 
of Smallwood (1909), who finds that the eggs arise 
in the entoderm in any region of the polyp, at the 
base, the side of the polyp, or in the gonophore. 
They may be distinguished from other entoderm 
cells by the larger size of the nucleus. 
In Pennaria cavolini the germ cells arise in the 
ectoderm, according to Weismann (1883), and this 
conclusion is confirmed for the ova by Hargitt 
(19045). In P. tiarella the germ cells are likewise of 
ectodermal origin (Smallwood, 1899, Hargitt, for 
the ova, 1904b). The eggs of this species arise 
in the ectoderm of the manubrium and grow by 
