18 CALIFORNIA ACADEMY OF SCIENCES. 



cells have none of the specialty of structures which 

 might be looked for, did sperm-cells and germ-cells need 

 endowing with properties essentially unlike those of all 

 other organic agents. On the contrary, these reproduc- 

 tive centers proceed from tissues that are characterized 

 by their low organization." 



Besides the accusation of producing unnecessary con- 

 fusion by the introduction of the mystical germ-plasm, 

 Ryder has a much more serious charge to prefer against 

 Weismann. He claims that the isolation of the germ- 

 plasma in the germ-cell is in conflict not alone with the 

 principles of metabolism, upon which modern physiology 

 stands, but also with the law of the conservation of en- 

 ergy. " Modern physiology," he says, "as well as the 

 doctrine of the conservation of energy, positively forbids 

 us to interpose any barrier between the plasma of the 

 parent-body and that of the germ-cells, as is done by the 

 promulgators of the hypothesis of the continuity and 

 isolation of the germ-plasma." What, then, is Ryder's 

 theory? Briefly this: All cells of the body have some 

 reproductive power, as shown by the healing of a wound 

 among the most specialized organisms, by the restora- 

 tion of a lost limb among lower forms, or of a lost organ, 

 as the eye, for example, by still lower, and by the power 

 of the lowest metazoa and some plants of forming a new 

 individual from a fragment of the parent. The lower in 

 the scale of life we penetrate, the more generally diffused 

 and potent do we find this regenerative power. The 

 logical inference from this is that reproductive force is 

 most powerful where the specialization is least. The 

 reproductive cells would accordingly be the least special- 

 ized cells of the body. Moreover, they are the only cells 

 which are normally passive and functionless. The spe- 

 cific molecular character of the reproductive cells, then, 

 according to Ryder, together with the molecular tenden- 



