Febrl'ARY 24, 1905.] 



SCIENCE. 



293 



that he should have had in mind in writing 

 them; yet without yielding to this tempta- 

 tion we may fairly pay our humble tribute 

 of admiration and homage to a scientific 

 insight that was capable of reaching such 

 a conclusion in the far away prehistoric 

 period when chromosomes and Mendelism 

 were unsuspected, when the nature of fer- 

 tilization was unknown, and the internal 

 mechanism of development was a wholly 

 unsolved riddle. 



I will in conclusion add only a few 

 words on the question of vitalism and 

 mechanism in the light of the foregoing 

 results. In so far as development may be 

 conceived as the outcome of an original 

 material configuration in the nucleus, and 

 a secondary configuration in the proto- 

 plasm, it may be conceived as a mechanical 

 process. But it must be admitted that 

 this conception leaves quite unsolved cer- 

 tain fundamental elements of our problem 

 — such, for instance, as the manner and 

 order in which the protoplasmic stuffs are 

 formed and assume their characteristic 

 configuration, whether in the whole egg or 

 in the isolated blastomere or egg-fragment ; 

 or again, how the wonderful phenomena of 

 the regeneration of lost parts in the adult 

 organism can be explained. We have at 

 present no positive data for an answer to 

 these questions. But it can hardly be dis- 

 puted that we have already made a con- 

 siderable advance towards a mechanical 

 solution of the problem, and if this be so, 

 by what right does the vitalist demand 

 that we shall adopt his hypothesis for the 

 portions still unsolved? Let us seek an 

 answer to this question in the answer to 

 a broader one. What is the object of the 

 study of development? I should state this 

 object somewhat as follows : First, to ob- 

 serve and to describe as completely and 

 simply as possible the actual phenomena of 

 development; secondly, to determine to 

 what extent, from its beginning in the egg 



to its completion in the adult organism, 

 the process can be formulated in terms of 

 the elementary laws of matter and of mo- 

 tion. But this is only a different way of 

 stating that our object is to ascertain in 

 what measure the operations of develop- 

 ment, under given external conditions, are 

 the result of an original configuration of 

 material particles in the egg. Now, I do 

 not need to say that even the approximate 

 accomplishment of these aims is still very 

 remote, their complete accomplishment im- 

 possible. I am fully in accord with the 

 neo-vitalists in their assertion that the phe- 

 nomena of development and of life gener- 

 ally have not yet been reduced to a me- 

 chanical basis, that they can not at present 

 be fully described in physico-chemical 

 terms. It is certain that living beings ex- 

 hibit structures more complex than any 

 existing in the inorganic world, and differ- 

 ent from them in kind. It is possible, 

 probable I believe, that living bodies may 

 be the arena of specific energies that exist 

 nowhere else in nature. I admit fully that 

 the interpretation of development I have 

 endeavored to outline does not exclude, but 

 in some ways actually si;ggests, the exist- 

 ence of such energies. I should, therefore, 

 even admit that the vitalists are wholly 

 right in their contention that the vital 

 processes are not at present explicable as 

 the direct result of such energies as are 

 observed in the non-living world. To pre- 

 judge this question would set up a dog- 

 matic barrier to progress, not only in biol- 

 ogy, but also in chemistry and physics. If 

 this be vitalism there are probably many of 

 us who must be enrolled as 'vitalists,' how- 

 ever doubtfully we may regard the honor 

 of bearing such a title. But if the word 

 'vitalism' be used in any other sense than 

 as a convenient phrase, an x by which to 

 designate an unknown quantity, if it be 

 taken in a positive sense to imply in the 

 living organism any negation of the funda- 



