Decemiier 29, 1911] 



SCIENCE 



903 



Heredity is a vain word. There are in it no 

 laws to be drawn forth, and consequently no 

 principles that can be stated. There are simply 

 certain curious remarks that may be made, some- 

 times for, sometimes against, the transmission of 

 virtues and vices by blood. And there are no 

 more cases for than against. 



Perhaps we may say that two chief 

 things have been discovered. One is that 

 there is a certain permanency of type in 

 living things, along with a certain dissec- 

 tibility, as it were, and a capacity for re- 

 combination in diverse ways. Certain 

 traits or characters seem to crystallize out, 

 and such crystallized units hold together, 

 and may be moved about, in the processes 

 of generation, according to certain rules, 

 from one individual to another, and com- 

 bined with other crystals from a diverse 

 source. Or, to change the figure, we find 

 the living world to be a web or net of defi- 

 nite, relatively permanent strands, that 

 interweave, that unite and separate, a 

 given strand pas.sing now into one individ- 

 ual, now into another; each individual pre- 

 senting a new combination of the strands; 

 a new knot in the web. And we have 

 worked out certain of the rules according 

 to which this interweaving takes place. 



The second great discovery is that of 

 some of the intimate material processes of 

 this interweaving. So far as we have gone, 

 we find that the strands which appear in 

 one view as personal characteristics, phys- 

 ical or mental, appear in another as mater- 

 ial processes, visible under the microscope ; 

 and the rules for the interweaving that we 

 discover by the study of one aspect of the 

 web we find faithfully followed when we 

 study the other aspect. This correspond- 

 ence seems to that unscientific wondering 

 individual which every man of science con- 

 ceals, one of the most astounding things in 

 science; it illustrates again the artless in- 

 genuousness of the popular idea that mat- 

 ter is something simple and well known, 



and that we deprive a phenomenon of its 

 wonder by showing that it takes place in 

 matter. "What happens in the personal 

 world finds its parallel, so far as we can 

 see, in the happenings of matter; the 

 wonder of the event is not increased or di- 

 minished whether we must call its medium 

 matter or something else equally mysteri- 

 ous and unfathomable; for nothing could 

 be more so. 



Our experimental science of genetics is 

 a phy.siology of the proces.ses by which new 

 generations are produced, comparable to 

 the physiology of metabolism — rather than 

 a study or doctrine of evolution ; although 

 we believe, and perhaps we see, that a 

 knowledge of it must precede any correct 

 understanding of evolution. Indeed, the 

 direct attacks hitherto made on the prob- 

 lem of how evolution occurs seem to owe 

 their relative lack of success to the fact 

 that they were not based on a knowledge of 

 the normal physiology of generation ; to 

 obtain this preliminary knowledge is now 

 the immediate task of investigation. But 

 this gives us as yet little or nothing that is 

 final on how the strands that make up the 

 living web arise, how they get their unity 

 and permanence, and how they are trans- 

 formed. Selection, mutation, environ- 

 mental action, formation of developmental 

 habits — each of these stands before us 

 with a question mark so large as to over- 

 shadow the word itself; experimentation 

 finds it equally difficult to confirm any of 

 them. 



But the existence and interweaving, ac- 

 cording to rules, of these relatively per- 

 manent strands, are what remain to 

 us positively. What is the relation of these 

 things to our own existence and person- 

 ality? 



As a material, potentially visible organ- 

 ism, I, like the infusorian, have been in 

 existence ever since the race that devel- 



