ALPEEUS HYATT, 18S8-1902 139 



One can not, however, establish a general law upon the study of a 

 highly specialized race of animals such as the shell-bearing cephalopods, 

 and we must search through the entire animal kingdom to thoroughly 

 test Hyatt's hypothesis; and zoologists have not yet done this, for the 

 paramount interest in studies of heredity now centers around Mendel's 

 law. Yet Hyatt has raised a burning question — is the course of evo- 

 lution a predetermined thing, and do the growth-stages of the indi- 

 vidual reveal to us the past, present and future of its race? Hyatt 

 says they do, for he states that organisms tend to produce offspring vary- 

 ing in a certain well-defined direction so that we may indicate with 

 tolerable certainty what species a given form can or might produce. 



It is sad to think that so few young men have followed him into 

 this great field of study, for a student's life is not wasted even if after 

 years of labor he discovers that his preconceived hypotheses were false 

 and he can not fathom nature's secrets, for it is not for science to advo- 

 cate, but only to search, hoping to discover. 



We will now take up the discussion of Hyatf s law of acceleration or 

 tachygenesis as he finally called it; although it was commonly known as 

 the "old age theory." According to Hyatt, modifications, once they 

 appear, tend to develop in successive generations at earlier and earlier 

 stages of growth, so that modifications which first appear in adult life 

 or even in old age before the animal becomes sterile will afterwards be 

 developed in the young stages of descendants. Finally, indeed, they 

 appear in the embryos or are crowded out and replaced by later charac- 

 ters, Hyatt believed this law of acceleration to be an invariable mode 

 of action of heredity. 



He also believed in the inheritance of acquired characters, and held 

 that the organism is plastic and irritable and responds to external stim- 

 uli by internal reactions which manifest themselves as hereditary modifi- 

 cations of structure. It is interesting to see that the recent researches 

 of Tower and MacDougal have shown that artificially produced changes 

 in the environment may affect the germ-cells and produce hereditary 

 modification of structure. 



Hyatt maintained that the evolution of new forms has been more 

 rapid than is generally supposed, and in this he has been supported by 

 the classic work of DeVries, who shows how suddenly a new form may 

 appear and maintain itself. It also accords with Bateson's demonstra- 

 tions of the frequency of " discontinuous variations." As Farlow says : 

 " Our so-called species are merely snap-shots at the procession of nature 

 as it passes along before us." 



Hyatt also states that the development of ancestral forms is usually 

 simple and direct; that of their more specialized descendants becomes 

 gradually indirect with complicated larval or intermediate stages; and 

 that of the terminal retrogressive stages, before extinction becomes again 

 more or less direct. Thus the last is like the first. 



