November 27, 1896.] 



SCIENCE. 



787 



mediate action of natural selection. It 

 is thus a phase of evolution without either 

 natural selection or the transmission of 

 acquired characters. I have no new facts 

 to bring forward, but wish to present 

 certain well-known facts in a new aspect 

 which has a very direct bearing upon 

 the theories of Spencer and Cope, as well 

 as of Weismann. The recent papers of 

 James Mark Baldwin contain something 

 very similar under the term Social Heredity. 

 It involves what the botanist, George Hen- 

 slow, has been calling 'Self-adaptation.' 

 In personal conversation Lloyd Morgan 

 has recently expressed to me very similar 

 views.* 



The matter rests upon well-known bio- 

 logical principles which may be expressed 

 in the following formula : 



FA^.^i+n^i /Congenital, Con 

 J i-ii?r^ = l stTtutional or 



/Conditions of Envi-\ 



w I ronment through- \ 

 -^1 out whole Period I 



/Adult Or-\ _ /^ 



/ \ ^''"t'- / ^ of Development. ' 



Every adult organism, therefore, has a 

 single set of characters, but each of these 

 characters has a double origin due to the 

 adjustments and readjustments of its inter- 

 nal and external relations in course of 

 growth. To sharply distinguish these two 

 origins, I some time ago proposed the terms 

 phylogenic and ontogenic, as in the follow- 

 ing table : 



VARIATIONS. 

 ONTOGENIC. PHYLOGENIC. 



Arising in course of de- Variations within the 



velopment from chemico- phylum, part of which 



physical, motor, psychi- were originally onto- 



cal (social and imitative) genie, 

 causes. 



Thus the really superficial or transient 

 differences between organisms are upon the 

 ontogenic side. The fundamental differ- 

 ences are phylogenic. The importance of 

 the discrimination between these origins 

 becomes apparent only when we realize 

 what profound modification occurs in the 

 course of ontogeny and how very generally 



*See Science, Nov. 20th. 



these modifications are confused with those 

 which really belong within the phj^lum. 



When we fully grasp the possibilities of 

 ontogenic variation it appears that onto- 

 genic evolution must be a leading, progres- 

 sive, guiding process, and is so far in ad- 

 vance of phylogenic evolution that in many 

 cases it gives rise to characters which we 

 use to separate species and even genera. 

 There is thus an individual evolution which 

 progresses under the following well-known 

 laws: (1) When the environment changes, 

 the adult individual changes, without neces- 

 sarily involving any alteration of the stirp. 

 (2) These ontogenic changes may be pro- 

 gressive or retrogressive, and reach a term 

 which we would give specific or generic 

 rank, as in the transformation of Artemia or 

 Saturnia. (3) A limited, if not complete, 

 internal adaptation must occur, because the 

 growth of every part of the organism de- 

 pends upon the nutritive materials supplied 

 to it as well as upon the stimuli which the 

 environment arouses. As shown in ex- 

 perimental embryology, a series of readjust- 

 ments of an adaptive character always 

 occur if the stimulus is not too profound. 

 (4) As to the external adaptation of the 

 organism to its surroundings in the strug- 

 gle for existence, it is apparent that chemi- 

 cal and physical changes do not necessarily 

 fit the organism. (5) Yet such purely 

 physical changes may be followed by asso- 

 ciated adaptations. Thus an animal shut 

 off from the action of light exhibits onto- 

 genic degeneration of pigment and of vision, 

 and, in general, of all organs which repre- 

 sent a response to light. This degenera- 

 tion is compensated by an increased sensi- 

 tiveness of the other sense organs of smell, 

 touch and hearing. (6) The most definite 

 adaptations arise as a result of new habits, 

 motions, etc. 



This principle of the ontogenic adap- 

 tive influence of habit is so well known, 

 it is surprising that more allowance for 



