66 The Unity of the Organism 



it is hardly possible to overestimate the importance of cor- 

 recting the method and neutralising the evil it has wrought. 



Weismanns Erroneous Conclusions Concerning the Origin 

 of Sex-Cells in Hydroids as an Example of the 

 Effect on the Observing Powers of the Germ- 

 Plasm Type of Speculation. 



A striking example of the effect of this system of specula- 

 tion on the observing and reasoning faculties is afforded by 

 Weismann's way of viewing the part played by the genn- 

 layers in bud propagation in young animals. We might 

 have presented the case when we were dealing with budding 

 in ascidians and bryozoans, but as it implicates germ-cells 

 and germ-plasm more intimately than we were prepared for 

 at that time we speak of it here. 



As pointed out above, Weismann's general interpretation 

 of the sex-cells in the hydromedusa^ led him to conceive that 

 the germ-plasm is lodged in the ectoderm in these animals. 

 This being so, he naturally concluded that his imaginary 

 bound C^gebu/nden*'), or unalterable, or accessory germ- 

 plasm set aside for bud propagation ("blastogenic germ- 

 plasm") must also be confined to the ectoderm. But ac- 

 cording to the various researches, both endoderm and ecto- 

 derm participate, as a rule, in giving origin to the bud. 

 What was to be done about this? Notice carefully what, 

 according to the system, would be a sufficient confirmation 

 of the theoretical view that buds really arise solely from 

 the ectoderm: To find one or a few instances in which the 

 buds do either certainly or probably begin in that layer, to 

 assume this to be the phylogenetically primitive condition, 

 and then to point out that in cases in which the two layers 

 undoubtedly enter into the bud in the earliest stage, the 

 "possibility is not excluded" that latent invisible germ-plasm 

 is present in the ectoderm, becomes active at the place where 



