THE EYES OF THE BLIND VERTEBRATES OF NORTH AMERICA. 197 



eye of the individual, is the result of functional adaptation during the lifetime of past 

 individuals to the total disuse of the eye. This adaptation, it was concluded, was 

 transmitted to a certain extent to the succeeding generation through the usual vehi- 

 cles of transmission. There has always been and is yet a serious objection to the 

 latter conclusion, because the method of the transmission of functional adaptations 

 to the organization of the egg so as to limit or extend its powers is not known. 



Recently, while admitting that functionally adaptive structures arise develop- 

 mentally without reference to function, Driesch ('99) has maintained that: "Wer 

 hier von 'Vererbung' friiher einmal functionell 'erworbener' Eigenschaften reden 

 will, verlasst den wissenschaftlichen Boden, denn wir wissen von solcher Art der 

 Vererbung gar nichts." 



Possibly we might find a warrant for the assumption of the transmission of func- 

 tional adaptation to the germ-cells in the writings of Driesch himself, though he might 

 not thank us for it. He maintains that certain developmental results whose prox- 

 imal cause he is not able to determine may be produced by factors working in a 

 distant part of the embryo. Without entering into a discussion of the validity of 

 these factors working at a distance, if they are really factors and capable of acting, 

 as Driesch imagines, why may not functional modifications effect changes in the 

 hereditary cells in a similar manner? 



I conclude that retardation and cessation in development are not due to 

 ontogenically operating causes, but they are inherent in the fertilized ovum and are 

 inherited. 



XVII. THE EYES OF AMBLYOPSIS AND THE LAW OF BIOGENESIS. 



During recent years the law variously termed von Baer's law, Agassiz's law, 

 Haeckel's law, or the law of Biogenesis, has been frequently called into question. Its 

 general tenets are : (1) Every individual in its development repeats in brief the devel- 

 opment of the race; (2) closely related forms have a similar ontogeny, and the nearer 

 two animals are related the longer their embryos are alike; (3) the embryos of high 

 animals pass through stages resembling the adult stages of lower animals; and (4) 

 in every ontogeny there are, among the truly ancestral stages, stages which are adap- 

 tive and have been acquired during ontogenic development. 



No objection has been raised to the fourth tenet in so far as its acceptance does 

 not commit to the acceptance of the first. In objection to the first of these proposi- 

 tions Hurst ('93, p. 399) writes: "I do not deny that a rough parallelism exists in 

 some cases between ontogeny and phylogeny. I do deny that the phytogeny can so 



