524 CHARLES W. HARGITT 
The fact remains, however, that Just these outgrown systems or 
theories still cumber the literature, the available text-books and 
manuals for introducing students to these subjects of present day 
biology, much to the reproach of its leaders and sponsors. 
With the desire to aid, in however small a degree, in correct- 
ing phases of error, or what appear such, the writer will aim under 
this section of the paper briefly to pass in review the chief aspects 
of the problems involved, and, so far as may be practicable, will 
endeavor to show distinctive examples of inadequate theory and 
erroneous implications and deductions. 
1. Origin, multiplication, and growth of germ-cells 
It seems worth while briefly to summarize results which obser- 
vations, more particularly my own, have brought to light on these 
several aspects of ontogeny. Many of the facts have already 
been made known in previous papers, but care will be taken to 
avoid, as far as may be, any unnecessary duplication, giving atten- 
tion chiefly to those features relating to phases which seem to 
‘all for consideration. Concerning the earlier controversy as to 
the mere place or tissue in which the germ-cells arise, it is no longer 
necessary to multiply words. Recent work from various sources, 
and especially that of Goette (07), has, I believe, placed the sub- 
ject beyond further dispute. That there is any such region as 
may be designated a ‘Keimzone’ or ‘Keimstiitte’ may be at once 
dismissed as absolutely without warrant as a general proposition. 
Furthermore, that the germ cells have their origin in the ecto- 
derm alone in hydromedusae may be similarly denied and dis- 
missed as unworthy of further inquiry or doubt. And still fur- 
ther, | am thoroughly convinced that the still more recent con- 
troversy as to the hypothesis of the ‘germ-plasm,’ if not as clearly 
a delusion as the preceding, is yet without the slightest support 
from the ontogeny of the group under review. 
It is a matter of easy demonstration that in many species of 
hydroids the egg may be followed in every detail from its origin as 
an ectoderm or an entoderm or interstitial cell through its gradual 
differentiation and growth to maturation, as a distinet individual 
