36 



SCIENCE. 



[N. S. Vol. I. No. 2. 



whether a variation is merely 'ontogenic,' 

 that is springing up in the course of indi- 

 vidual development from some disturbance 

 of the hereditary mechanism, or 'phjlogenic^ 

 and constant as distinguished by Nageli. 

 From recent study of palingenic variation 

 we must recast our conception of Heredity 

 especially in view of the remai-kable re- 

 searches of Cunningham upon the color, 

 and of Agassiz, Giard and Filhol upon the 

 sjrmmetry of the flat fishes (Pleuronec- 

 tidse). These characters of enormous an- 

 tiquity, summoned as it were from the vasty 

 deep, reveal the law that repetition or vari- 

 ation in ontogeny depend largely upon 

 repetition or variation in environment, that 

 for many of the most fundamental charac- 

 ters, development and environment are 

 inseparable and all theories which tend to 

 separate the tv\'0 are untenable. As regards 

 cenogenic variations or those which are 

 new in the experience of the organism, the 

 distinction between ontogenic variations, or 

 what are commonly called acquired chara- 

 cters, and phylogenic variations is also of 

 pressing importance. The organism may 

 be compared to a clock, keeping regular time 

 upon a base ; if the base is tilted slightly 

 the clock may continue to tick but it may 

 not keep the same time ; if after the lapse 

 of a long period the base is restored to its 

 original position the clock will tick in cor- 

 rect time as before. This thought shows 

 that the conditions which have been de- 

 manded as crucial tests of the permanent 

 phylogenic influence of environment upon 

 organisms will be very difficult to fulfill in 

 experiment — when the repetition of a meso- 

 zoic environment is found to produce a repe- 

 tition of a mesozoic structure. Experiment 

 should now be directed separately iipon 

 each of the four stages of development 

 (germ cell, fertilization, embryonic, larval 

 and adult) and then withdi'awn, and put- 

 ting together the results of all the work 

 which has been recently done of this kind 



we find three classes of variation phenomena 

 coming to the surface ; first 'palingenic 

 variations,' second 'saltations,' thu-d 'onto- 

 genic adaptions' (Haeckel); fourth a class 

 of 'phylogenic variations' which have been 

 termed 'mutations' by some jjaleontologists. 

 We are so far from a sohition of the work- 

 ing causes of these four classes of variation 

 that it seems best to consider that we are 

 on the threshold of the Evolution Problem, 

 to take an entirely agnostic or doubtful posi- 

 tion as to all the prevalent theories, and press 

 forward in strictly inductive search for laws 

 which maj' not be forthcoming imtil the 

 next centviry. 



Professor Edmund B. Wilson, of Columbia 

 College, followed with a discussion of the 

 influence of the environment on the early 

 stages of embryonic development. That a 

 change of external conditions, such as tem- 

 perature, chemical nature of the medium and 

 the like, causes changes in the rate or form 

 of development has long been a familiar 

 fact, but we have only recently come to per- 

 ceive clearly how significant are the changes 

 thus broiight about and how vital is the part 

 played by the environment in all develop- 

 ment, whether pathological or normal. For 

 if a changed mode of development is the 

 ' result ' of a change of envu-onment, the 

 normal development must in exactly the 

 same sense be the ' result ' of the normal en- 

 vironment, i. e., in both cases we are deal- 

 ing with a definite phj^siological response of 

 the idioplasm to external conditions. The 

 facts both of normal and of experimental 

 embryology demonstrate the justness of this 

 point of view. The experiments of Pfliiger, 

 Driesch, Eoux and others show, for instance, 

 that the forms of cleavage may be pro- 

 foundljr altered by mechanical means, and 

 indicate that some of the normal fundamen- 

 tal cleavage-forms are the direct result of 

 mechanical conditions, such as the shape of 

 the egg, pressure of the membranes, surface 

 tensions between the blastomeres, and the 



