346 THE AMEEICAN NATURALIST [YOL. LIII 



tion of misplaced, supernumerary and other useless 

 structures, and the occurrence of anaphylaxis, instead of 

 immunization, certainly do not argue for the existence 

 of a primary teleology" in nature, though, of course, 

 they do not wholly refute it. 



On the other hand, the occurrence of these non-adaptive 

 responses to growth stimuli is no more inconsistent with 

 an intra-selection hypothesis, such as that here advo- 

 cated, than is the occurrence of multitudes of non- 

 adaptive structures or colors in nature inconsistent with 

 the theory of natural selection. There must be rigid 

 limitations to the operation of both processes. The task 

 which I have undertaken here is not to explain structures 

 and function in general, but the more modest one of try- 

 ing to explain why certain among these are directed to- 

 ward the conservation of the individual or the species. 

 If various other vital phenomena are found to be non- 

 adaptive, our difficulties ought not to be increased. 



There are cases, it is true, in which some simple phys- 

 ical factor, such as gravity, or the plane of section, may 

 determine whether the actual missing part is restored or 

 a misplaced organ is the result. It certainly seems arbi- 

 trary to offer fundamentally different explanations in 

 the two cases. Now, I have nowhere made the conten- 

 tion that the processes involved in regeneration are 

 w^holly random, in the sense of being unrelated to one 

 another and to the past history of the individual. In 

 normal development the processes are doubtless so con- 

 catenated that growth and differentiation proceed in a 

 direct way with little or no ''lost motion." And every 

 detached portion of such an organism must receive its 

 share of this established developmental machinery. The 

 tendency to reconstruct the whole, to attain the normal 

 specific form, is therefore opposed by another set of 

 tendencies, urging it to develop as if it were still part of 

 the undivided organism. As is well kno^\^l, the outcome 

 of this conflict of forces varies, depending upon the spe- 

 cies of animal and the time of operation. We may have 



