238 The Science of Life. 



mann has gone one better still. One must pass through 

 these stages and appreciate their strength before one 

 sees their weakness, and becomes, at each transition, a 

 sceptic of a higher order. It is difficult to abbreviate 

 the intellectual ontogeny, except in the course of gener- 

 ations. Thus, Weismannism seems vanity and vex- 

 ation to those who have never found the limits of 

 Lamarckianism, nor strained at the Darwinian tether. 

 Undoubtedly the various stages will seem larval enough 

 some day. 



But to all who have tried to sound the depths not 

 altogether pellucid of modern aetiology, one result at 

 least should be clear that we need to get back to 

 facts. We fully recognize the value of speculative 

 interpretation, of logical dialectics, even of controversy 

 with what Spencer calls "its terrible fertility, and 

 unmanageable population of issues, old and new, which 

 end in being a nuisance to everybody"; but periodically 

 there must be a re-examination of the basis of fact. 

 Perhaps Weismann's greatest service after all, and in 

 part because of the masterliness of the theory, will be 

 in forcing biologists back to experiment. 



It seems needless to suggest that there should be a 

 pause in speculation. For we need all the suggestions 

 we can get, and the intellectual speculator will not be 

 discouraged whatever one may say. At the same time, 

 it becomes tiresome to wade through the flood of 

 aetiological literature when one observes how much of 

 it might have been spared us, if the writers had only 

 read the Origin of Species more carefully, or taken the 

 trouble to understand Weismann. 



It is also fair to recognize that there has already 

 been a fair amount of experimenting. But relatively 

 little of it has had any direct reference to the factors 

 of evolution. It is recognized on all sides that what 

 we now require is a period of experimental evolution. 



Among the lines of observational and experimental 

 work which are open or have been opened, the follow- 

 ing may be noted: 



(i) Experiment and observation on the nature of 

 variations (e.g. Bateson's work). 



