398 POPULAR SCIENCE MONTHLY. 



organ in the individual may be crowded (ontogenetic — Roux). This 

 may lead to the development of the used organ as against the disused 

 through a compensation of growth (Goethe, Saint-Hilaire, Roux); this 

 ontogenetic result becomes phylogenetic through transmission of the 

 acquired character (Roux), or is in its very nature phyloblastic (Kohl). 



5. Through the struggle between soma and germ to produce the 

 maximum of efficiency of the former with the minimum expenditure 

 to the latter (ontogenetic and phylogenetic — Lendenfeld). 



6. Through germinal selection, the struggle of the representatives 

 of organs in the germ (ontogenetic and phylogenetic — Weismann). 



The idea of ontogenetic degeneration is intimately bound up with 

 the idea of phylogenetic degeneration. Logically we ought to consider 

 first the causes of individual degeneration, and then the processes or 

 causes that led to the transmission of this. Practically it is impossible 

 to do so, because many of the explanations are general. Only No. 4 of 

 the above may be taken in the ontogenic sense purely, though it was 

 certainly also meant to explain phylogenetic degeneration. In many 

 of the explanations of particular cases of degeneration more than one of 

 the above principles are invoked, though only one was meant to be used. 

 In most cases, however, the discussions of degeneration have been in 

 general terms, without direct bearing on any specific instance of de- 

 generation in all its details. It must be evident that such discussions 

 can only by accident lead to right results. 



By the Lamarckian ontogenetic degeneration is considered the result 

 of lack of use and consequent diminished blood supply. The results of 

 the diminution caused by the lack of use during one generation are 

 transmitted in some degree to the next generation, which thus starts at 

 a lower level. A continuation of the same conditions leads finally to 

 the great reduction and ultimate disappearance of an organ. 



No one, so far as I am aware, has succeeded in accounting for the 

 degeneration of the eye by means of this view. Packard's* explanations 

 are evidently a mixture of Lamarckism and Darwinism. 



Packard says: "When a number, few or many, of normal-seeing 

 animals enter a totally dark cave or stream, some may become blind 

 sooner than others," some having the eye slightly modified by disuse, 

 while others may have in addition physical or functional defects, espe- 

 cially in the optic nerves and ganglia. "The result of the union of such 

 individuals and adaptation to their Stygian life would be broods of 

 young, some with vision unimpaired, others with a tendency to blind- 

 ness, while in others there would be noticed the first steps in degenera- 

 tion of nervous power and nervous tissue." Packard evidently had in- 

 vertebrates in mind. He clearly admits the cessation of selection or 



* American Naturalist, September, 1894, vol. xxviii, p. 727. 



