189 6.] On Heredity and Rejuvenation. 93 



The development of an organism- does not depend on a substance 

 stored in special cells, but on a special condition (stage) of organi- 

 zation. As a corollary of this hypothesis may be given this 

 conclusion : Germ plasm, in Weismann's sense, does not exist. 



According to my view, every part inherits from the germ, 

 and every part of the animal body, as well as its germ cells, 

 possesses the multiplying morphogenetic force, the action of 

 which, however, is inhibited to the condition of the parts 

 themselves. What this condition may be is not yet exactly 

 known, but this much we do know, that the morphogenetic force 

 is found in full activity in cells with little protoplasm. It is in- 

 deed highly probable that the slight development of proto- 

 plasm in proportion to the nucleus is an unavoidable condi- 

 tion of morphogenesis, or in other words, of the action of her- 

 edity. In fact we see that the first processes of development 

 — as I have elsewhere explained (Proc. A. A. A. S., XIX) — 

 show in the most varied cases a remarkable uniformity, for 

 they always accomplish the production of cells with little pro- 

 toplasm. Compare, in this respect, the vegetation points of 

 plants, the root buds of slips, the budding zones of Annelids, 

 the germinal layers of vertebrates, etc. The condition which 

 allows the morphogenetic or hereditary force to act, arises 

 under differing conditions, of which the fertilization of the 



Weismann tries to make comprehensible to us this one case, 

 that of the fertilized ovum, by a special explanation which is 

 available for no other case. Oscar Hertwig has recently (Zeit 

 und Streitfragen, Heft I) clearly shown that Weismann's ex- 

 planation is a speculative assumption, which can only, be 

 saved from rejection by numerous and often selfcontradictory 

 additional assumptions. As I fully agree with Hertwig's crit- 

 icism, I need only refer to his essay. 



We will return to our proper theme. The next point is to 

 determine whether there is a difference in the condition of 

 the cells, as, regards their capacity for development, between 

 larvte, on the one hand, and embryos on the other. It can be 

 proved that this is the case, by the following considerations. 

 So far as we vet know, it is chiefly two factors which inhibit 



