PORIFERA, CHELENTERATA, VERTEBRATA 95 
into the endoderm. Something must be lacking in 
the endoderm that is necessary to make a cell into a 
germ-cell: that something is the germ-plasm.” 
Several important contributions have appeared 
within recent years which seem to deprive Weis- 
mann’s contentions of much of their importance. 
For example, Goette (1907) has found that the germ 
cells of many Hypromepts.£ may arise in the en- 
toderm or in the ectoderm, and that in Clara multt- 
cornis the germ cells are transformed half-entoderm 
cells. After a long series of studies on ccelenterate 
development C. W. Hargitt (1911) has attacked 
Weismann’s position in the following words: ‘‘ That 
there is any such region as may be designated a 
“Keimzone’ or ‘Keimstitte’ may be at once dis- 
missed as absolutely without warrant as a general 
proposition. Furthermore, that the germ cells have 
their origin in the ectoderm alone in hydromeduse 
may be similarly denied and dismissed as unworthy 
of further inquiry or doubt. And still further, I am 
thoroughly convinced that the still more recent 
controversy 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. 
“Tt 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 distinct individual 
cell, without the slightest tendency to multiplication.” 
