TRANSACTIONS OF SECTION 11. 7G7 



to one's clearness of perception of this much-discussed question if one defines at 

 the outset in wliat sense the term ' acquired characters ' is employed ; and it is the 

 more advisable that this should be done, as the expression has'not always been 

 used with the same siprnification This term may be used in a wide or in a more 

 restricted sense. In its wider meaninfr it may cover all the characters which 

 make their first appearance in an individual, and which are not found in its 

 parents, in whatever way they have arisen : — 



1st. Whether their origin be due to such molecular changes in the germ-plasm 

 as may be called spontaneous, leading to such an alteration in its character as may 

 produce a new variation ; or, 



2nd. Whether their origin be accidental, or due to habits, or to tha nature of 

 the surroundings, such as climate, food, &c. 



Professor Weismann has pointed out with great force the necessity of distin- 

 guishing between these two kinds of ' acquired characters,' and he has suggested 

 two terms the employment of which may keep before us how important it'"]! that 

 these dlflerent modes of origin should be recognised. Characters which are pro- 

 duced iu the germ-plasm itself by natural selection, and all other characters which 

 result from this latter cause, he names bladogenic. He further maintains that all 

 blastogenic characters can be transmitted ; and in this conclusion, doubtless, most 

 persons will agree with him. On the other hand, he uses the term .somatoffenic 

 to express those characters which first appear in the body itself, and which follow 

 from the reaction of the goiua under direct external influences. lie includes under 

 tliis head the effects of mutilation, the changes which follow from increased or 

 diminished performance of function, those directly due to nutrition, and any of the 

 other direct external influences which act upon 'the body. lie further maintains 

 that the somatogenic characters are not capable of transmission from parent to 

 offspring, and he suggests that iu future discussions on this subject the term 

 'acquired characters ' should be restricted to those which are somato"-enic. 



Thus one might say that blastogenic characters arising in the g'erm would be 

 acquired in the individual by the action of the germ upon the soma ; so that if we 

 return again to the graphic illustration previously employed, the germ-pla-sm repre- 

 sented by the small italic letters abed would act upon the soma represented by 

 the capital letters A, B, C, D. Somatogenic characters, again, arising in the soma, 

 ■would be acquired by the action of the soma A, B, C, D, upon the contained germ- 

 plasm abed. But whether those acquired characters expressed by the term 

 somatogenic can or can not be transmitted has been fruitful of discussion. 



That the transmission of characters so acquired can take place is the foundation 

 of the theory of Lamarck, who imagined that the gradual transformation of species 

 was due to a change in the structure of a part of an organism under the influence 

 of new conditions of life, and that such modifications could be transmitted to the 

 offspring. It was also regarded as of importance by Charles Darwin, who stated • 

 that all the changes of corporeal structure and mental power cannot be exclusively 

 attributed to the natural selection of such variations as are often called spon- 

 taneous, but that great value must be given to the inherited effects of use and dis- 

 use, some also to the modification in the direct and prolonged action of changed 

 conditions of life, also to occasional reversions of structure. Herbert Spencer 

 believes - that the natural selection of favourable varieties is not in itself suflicient 

 to account for the whole of organic evolution. He attaches a greater importance 

 than Darwin did to the share of use and disuse in the transmission of variations. 

 He believes that the inheritance of functionally produced modifications of structure 

 takes place universally, and that as the modification of structure by function is a 

 vera caum as regards the individual, it is unreasonable to suppose that it leaves no 

 traces in posterity. 



On the other hand, there are very eminent authorities who contend that the 

 somatogenic acquired characters are not transmissible from parent to offspring. 

 Mr. Francis Galton, for example, gives a very qualified assent to the possibility of 



L 



Preface to 2nd edition of Dwent of Man, 1885; also Oriyhi of Spcciet, 1st ed 

 ' factors of Organic Evolution,' Nineteenth Century, 1886. 



