Sept. 26, 1889] 



NATURE 



531 



In connection with the tendency to the transmissibility of 

 •either congenital malformations or diseases, consanguinity in 

 the parents, although by no means a constant occurrence, is a 

 factor which in many cases must be taken into consideration.^ 

 If we could conceive both parents to be physiologically perfect, 

 then it may be pr2sum»d that the offspring would be so also ; 

 but if there be a departure in one parent from the plane of 

 physiological perfection, then it may safely be assumed that 

 either the immediate offspring or a succeeding generation will 

 display a corresponding departure in a g'-eater or less degree. 

 Should both parents be physiologically icaperfect, we may expect 

 the imperfections if they are of a like nature to be intensified 

 in the children. It is in this respect, therefore, that the risk of 

 •consanguineous marriages arises, for no family can lay claim to 

 physiological perfection. 



When we speak of tendencies, susceptibilities proclivities, or 

 predisposition to the transmission of characters, whetlier they be 

 normal or pathological, we employ terms which undoubtedly 

 have a certain vagueness. We are as yet quite unable to recog- 

 nize, by observation alone, in the germ-plasm any structural 

 change which would enable us to say that a particular tendency 

 or susceptibility will be manifested in an organism derived from 

 it. We can only determine this by following out the life-history 

 of the individual. Still it i-; not the less true that these terms 

 express a something of the importance of which we are all 

 consc'ous. So far as Man is concerned, the evidence in favour 

 of a tendency to the transmission of both structural and functional 

 modifications which are either of dis-service, or positively in- 

 jurious, or both, is quite as capable of proof as that for the 

 transmission of characters which are likely to be of service. 

 Hence useless as well as useful characters may be selected and 

 transmitted hereditarily. 



I have dwelt somewhat at length on the transmissibility of 

 useless characters, for it is an aspect of the subject which more 

 especially presents itself to the notice of the patholo:;ist and 

 physician ; and little, if at all, to that of those naturalists whose 

 studies are almost exclusively directed to the CKamination of 

 organisms in their normal condition But when we look at Mm, 

 his diseases form so large a factor in his life that they and the 

 effects which they produce cannot be ignored in the study of his 

 nature. 



Much has been said and written during the last few years of 

 the transmission from parents to off-;pring of characters which 

 have been " acquired " by the parent, so that I cannot altogether 

 omit some reference to this subject. It will conduce to one's 

 clearness of perception of this much-discussed question if one 

 defines at the ou'set in what sense the term " acquired charac- 

 ters" is employed ; and it is the more advisable that this should 

 be done, as the expression has not always been used with the 

 same signification. This term may be used in a wide or in a 

 'more restricted sense. In its wider meaning 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 — 



(i) 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, 



(2) Whether their origin be accidental, or due to habits, or to 

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



Prof. Weismann has pointed out with great force the necessity 

 of distinguishing between these two kinds of "acquired charac- 

 ters," and he has suggested two terms the employment of which 

 may keep before us how important it is that these different 

 modes of origin should be recognized. Characters which are 

 produced in the germ-plasm itself by natural selection, and all 

 other characters which result from this latter cause, he names 

 blastogenic. He further maintains that all blastogenic characters 

 <;an be transmitted ; and in this conclusion, doubtless, most 

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

 •the term snnatogenic to express those characters which first 

 appear in the body itself, and which follow from the reaction 

 of the soma under direct external influences. He includes under 

 this 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 



' I may esp'cially refer for a discussion of this subject to an adTiirabla 

 essay, by S.r Arthur Mitchell, K.C.B , "'Oa Blood Relationship in Marriage 

 considered in its Influence upon the Offspring." 



which act upon the body. Hi further maintains that the somato- 

 genic characters are not capable of transmission from pirent to 

 offspring, and he suggests that in future discussions on this subject 

 the term "acquired characters" should be restricted to those 

 which are somatogenic. 



Thus one might say that blastogenic characters arising in the 

 germ 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-plasm represented by 

 the small italic letters ahcd would act upon the soma repre- 

 sented by the capital letters A, B, C, D. Somatogenic charac- 

 ters, 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 acquire 1 can take 

 place is the foundation of the theory of Lamarck, who imagined 

 that the gradual transformation of species was due to a chan je 

 in the structure of a part of an organism under the infl lence of 

 new conditions of life, and that such modifications could be 

 transmitted to the offspring. It was also regarded as of import- 

 ance 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 spontaneous, but that great value mast be given to the 

 inherited effects of use and disuse, some also to the modifica- 

 tion in the direct and prolonged action of chanT;ed conditions 

 of life, also to occasional reversions of structure. Herbert 

 Spencer believes- that the natural selection of favourable 

 virieties is not in itself sufficient 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 eaiisa 

 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 transmis- 

 sible from parent to offspring. Mr. Francis Galton, for example, 

 gives a very qualified assent to this proposition. Prof. His, of 

 Leipzig, doubts its validity. Prof Weisnannsays that there is no 

 pro )f of it. Mr. Alfred Kussel Wallace, in his most recent work,-* 

 considers that the direct action of the environment, even if we 

 admit that its effects on the individual are transmitted by inherit- 

 ance, are so small in comparison with the amount of spontaneous 

 variation of every part of the organism that they must be qaite 

 over-shadowed by the latter. Whatever other causes, he says, 

 have been at work, natural selection is supreme to an extent 

 which even Darwin himself hesitated to claim for it. 



There is thus a conflict of opinion amongst the authorities 

 who have given probably the most thought to the consideration 

 of this question. It may appear, therefore, to be both rash and 

 presumptuous on my part to offer an opinion on this subject. I 

 should, indeed, have been slow to do so had I not thought that 

 there were some aspects of the question which seemed not to 

 have been sufficiently considered in its discussion. 



In the first place, I would, however, express my agreement 

 with much that has been said by Prof. Weismann on the want 

 of sufficient evidence to justify the statement that a mutilation 

 which has affected a parent can be transmitted to the offspring. 

 It is, I suppose, within the range of knowledge of most of us 

 that children born of parents who have lost an eye, an arm, or a 

 leg, come into the world with the full complement of eyes and 

 limbs. The mutilation of the parent has not affected the off- 

 spring ; and one would, indeed, scarcely expect to find that such 

 gross visible losses of parts as take place when a limb is removed 

 by an accident or a surgical operation should be repeated in the 

 offspring. But a similar remark is also applicable to such minor 

 mutilations as scars, the transmission of which to the offspring, 

 though it has been stoutly contended for by some, yet seems not 

 to be supported by sufficiently definite instances. 



I should search for illustrations of the transmission of somato- 

 genic characters in the more subtle processes which affect living 

 organisms, rather than those which are produced by violence 



' Preface to second edition of "Descent of Mm," 1885; alsj " Origin o 

 Species," first edition. 

 ^ '• Factors of Organic Evolution," Nineteenth Century, 1886. 

 3 "Darwinism," p. 443 (London, 1889). 



