96 GERM-CELL CYCLE IN ANIMALS 



"It is passing strange that he should ignore the 

 body of facts concerned in regeneration, and among 

 them the reproductive organs. And it is still more 

 strange that in support of this he should cite in 

 detail the Hydrozoa as illustrating and supporting 

 the hypothesis, ignoring the well-known facts that 

 among these are abounding evidences which afford 

 insuperable objections to just these assumptions. 

 The present author has, in many cases, shown that 

 gonads may be as readily regenerated by hydroids 

 and medusae as any other organs ; and that not for 

 once or twice, but repeatedly in the same specimen, 

 and that de novo and in situ; not the slightest evi- 

 dence being distinguishable that any migration 

 through preexisting * germ-tracks ' occurred. The 

 assumption that in these animals the gonads have 

 * been shifted backwards in the course of phylogenetic 

 evolution, that is, have been moved nearer to the 

 starting point of development ' seems so at variance 

 with known facts as to be difficult to appreciate or 

 respect." 



Professor Hargitt finally concludes with the fol- 

 lowing sentence : "I believe the foregoing facts 

 must suffice to show that, both as to origin, differen- 

 tiation, and growth, the germ-cells of the Hydrozoa, 

 so far from sustaining the doctrine of the germ- 

 plasm, afford the strongest and most direct evidence 

 to the contrary." 



G. T. Hargitt (1913) has also discovered facts 

 regarding the history of the germ cells in coelenter- 

 ates which are decidedly opposed to Weismann's 



