May 18, 1906.] 



SCIENCE. 



787 



As has frequently, though not always, been 

 recognized in discussions of organic selection, 

 the guidance of evolution, through plastic 

 modifications of the individual, is not exact. 

 The frequently used illustration of the forced 

 adoption of an arboreal habit by individuals 

 of a monkey-like species, vphen environmental 

 conditions became unsuitable for their per- 

 sistence upon the ground, recognizes that this 

 ontogenetic change of habit will not guide to 

 the evolution of an innate tree-climbing in- 

 stinct. For example, in Conn's use of this 

 illustration, the tree-climbing habit leads to 

 the survival of individuals which show en- 

 tirely different congenital adaptation, modi- 

 fications in foot and hand structure. Here 

 a change to a tree-climbing habit has had a 

 general influence, making all adaptation for 

 life in the trees advantageous. The efFect is 

 general and the effect upon evolution is gen- 

 eral, not preserving congenital adaptations 

 similar to the first ontogenetic adaptation, but 

 preserving entirely different sorts of adapta- 

 tions. The effect is vague and general. It 

 is, however, no less real. 



In a species whose members are slightly 

 plastic, or slowly responsive to modifying 

 influences, innate characters, similar to those 

 ontogenetically acquired, may be evolved, but 

 in a species whose members are highly plastic 

 and rapidly responsive, the adaptive innate 

 characters which may later be produced, will 

 probably be of a type different from that of 

 those ontogenetically acquired. In other 

 words, the greater the plasticity, the less inti- 

 mate will be its guidance of the course of evo- 

 lution, for a rapidly acquired and highly de- 

 veloped ontogenetic adaptation is almost as 

 beneficial as an innate adaptation of the same 

 type. 



There is another possible influence of plas- 

 ticity, which is worth considering. There is 

 some paleontological evidence in favor of a 

 belief that there are definite trends in evolu- 

 tion, due to conditions within the organism, 

 rather than to external factors. I have, in 

 this journal, pointed out' that the appearance, 



'Science, N. S., Vol. XXI., No. 531, March 3, 

 1905. 



generation after generation, of the same 

 mutants of (Enoihera lamarchiana, in num- 

 bers far greater than could be explained by 

 purely fortuitous variation, is a further indi- 

 cation of some internal control over variation, 

 making it somewhat determinate, instead of 

 purely indeterminate. Weismann's theory of 

 germinal selection is an ingenious explanation 

 of a possible way in which such trends in evo- 

 lution may arise and persist. I believe there 

 is evidence that well-defined trends in evolu- 

 tion have existed (paleontological evidence) 

 and do exist (evidence from CEnothera la- 

 marcJciana) . This question could be settled by 

 sufficiently prolonged and sufficiently exten- 

 sive observations in breeding, to see if varia- 

 tions and mutations do tend to be grouped in 

 particular directions rather than to be equally 

 distributed in all directions from the mean. 



If it be true that trends in variation (or 

 in evolution, the same thing) do exist, it 

 suggests an interesting consideration in con- 

 nection with plasticity. If such trends do 

 exist, it is probable that they will appear in 

 a species, persist for a time and ultimately 

 die out. It is, therefore, possible that the 

 adaptability of the individual members of a 

 species might tide the species over a period 

 of disadvantageous environmental conditions, 

 giving time for some new and advantageous 

 trend to appear. Such an effect is not only 

 conceivable; it seems not unlikely that in 

 numerous instances it may have been im- 

 portant. Maynard M. Metoalf. 



The Woman's CoLtEOE of Baltimoke, 

 March 6, 1906. 



A SIMPLE FORMULA FOR MIXING ANY GRADE OF 

 ALCOHOL DESIRED. 



This problem of mixing different grades of 

 alcohol recurs almost periodically to the work- 

 er in biology, but at sufficiently long inter- 

 vals for him to forget his method. I do not 

 recall, on the other hand, that I have ever seen 

 any wholly satisfactory rule or formula that 

 was simple, easy to remember, and with which 

 one could, at a glance, mix any desired 

 quantity, or having given a certain volimie of 

 any grade of alcohol, that one could with readi- 

 ness change the whole volume into the required 



