HEUEDITY 



C79 



roust be confessed, however, that, in default of fresh 

 experiment**, cogent evidence to negative \\ 

 niann's scepticism is Htill awanting, tliough Bonie 

 .-lU'^fst i vt- arguments in support of the old fashioned 

 Ill-lift' in ill-- inhfi ii-un-i- of acquired charoctere 

 are forthcoming, especially perhaps in connection 

 \\itli instinct and tfie growth of intelligence. (<t) 

 Aimtlier inoilf of argument often adopted against 

 NVeisinann's conclusion is to shift the ground to 

 the study of evolution, and there to demonstrate 

 .-'|i> of progress which seem to many inexplicable 

 on Weisinaiiii's sole formula of natural selection 

 acting on variations produced by the intermingling 

 of male and female germ-plasmas in fertilisation. 

 (e) Finally, it may he urged that the unity of the 

 organism, tin- connectedness of its elements, the 

 .minion inf.liiim of the blood, and other facts 

 m.ilvf it .lillicnlt to believe that the germ-plasma 

 can live on in the reproductive organs, unchanged 

 by any of the deep environmental and functional 

 variations which sometimes modify the structure 

 of the body. Those who seek to maintain the 

 transmission of some acquired characters have 

 obviously to submit their cases to all the stern 

 criticism which VVeismann's valuable work in- 

 volves. But if such cases be proved, it need not, 

 of course, lead to any departure from some form of 

 the doctrine of continuity, on which Weismann 

 has so well insisted, nor to a return to the supposi- 

 tion of travelling ' pangenes.' It does not affect 

 the theory of continuity to admit that decisive 

 variations produced by environment Or function 

 may send their roots deep into the system, pene- 

 trating through the body to the reproductive cells 

 themselves. Such cases are confessedly at present 

 dubious, but there is no a priori reason why the 

 ex-cells should not share in the results of altered 

 nutriment and waste products, and even become 

 saturated or infected by the characteristic chemical 

 results of environmental and functional variations. 

 Social Aspects. All the important biological 

 Conclusions, siich as that of germinal continuity, 

 or the fact that the two parents contribute almost 

 equal shares to the starting of the offspring, and 

 also the scepticism about the transmission of 

 acquired characters, have an obvious human in- 

 terest. The first result enables us to realise that 

 the germ is virtually as old as the parent, and that 



Fig. 3. 



A- A*, the liodies of successive generation.*; o-o', the germ-cells 

 between which the real continuity obtains. 



the main line of hereditary connection is not that 

 between parent and child, but ' that between the 

 sets of elements out of which the personal parents 

 had l>een evolved, and the set out of which the 

 personal child was evolved.' 'The main line/ 

 Gallon savs, ' may lie rudely likened to the chain 

 of a necklace, and the personalities to pendants 

 attached to the links.' To this fact social inertia 

 is largely due, for the organic stability secured by 

 gfrininal continuity hinders evolution by leaps 

 and bounds, either forwards or backwards. That a 

 good stock is pre-eminently valuable U an obvious 

 truth. The fact that each parent contributes 

 almost equally to the olfspring emphasises the 

 two sided responsibility of parentage; but the fact 

 has to l>e corrected by Gallon's statistical conclu- 

 sion that the offspring inherits a fourth from each 

 parent, and a sixteenth from each grand-parent. 

 Inherited capital is thug not merely dual, but 

 multiple, like a mosaic. Again, if we Itelieve with 

 Weismann that no acquired characters are in- 

 herited, we are saved from the despair which the 

 abnormal functions and environments of our 



civilisation are apt to Htigge*t. But if the inllu- 

 enceH of function and environment do not readily 

 become entailed or ingrained, we are all the more 

 in -i-d to practical action, which will secure im- 

 |.i.i\fi| condition* of life for each tmccuKhive crop 

 of individuals. 



The fact that pathological conditions innate or 

 congenital in an organism certainly tend to be 

 transmitted suggest* that popular opinion should 

 be informed ana educated an to midexirahility of 

 parentage on the part of abnormal members of the 

 community. All congenital malformation* and 

 defects due to germinal faults tend to he trans- 

 mitted, and the list includes not a few of evident 

 practical importance, such as poverty of teeth, 

 abnormal fingers, harelip and cleft-palate, and 

 , defective sense-organs. Still more important, how- 

 ever, are congenital or constitutional, as opposed 

 to acquired, diseases. Certain forms of insanity 

 and diseases of the nervous system and sense- 

 organs, deaf-mutism, colour-blindness, gout, mus- 

 cular weakness, unusual liability to certain con- 

 tagious diseases, tendencies to consumption, cancer, 

 and dipsomania, are illustrations from a long list 

 of inheritable diseases or weaknesses. Some dis- 

 eases are transmissible with greater probability 

 than others i.e. in a larger percentage of cases; 

 some appear to take a firmer grip of the constitu- 

 tion, ana may persist for many generations, while 

 others are more readily counteracted or ' washed 

 out ' by hygienic regime or by intercrossing ; some 

 are transmitted along tolerably constant lines e.g. 

 father, daughter, grandson i.e. in alternate sexes, 

 or father, son, grandson i.e. along similar sexes, 

 while others are quite irregular in their occurrence. 

 In reference to lines of transmission, Galton is 

 inclined to conclude that ' the female influence is 

 inferior to that of the male in convey ing-ability.' 

 In the case of a disease like consumption, which 

 decimates our British population, it ought to be 

 noted that in about 50 per cent, of cases it is in- 

 dividually acquired, not inherited ; that, as the 

 disease is bacterial, only a consumptive tendency 

 at most is transmitted ; that, even when the phthisis 

 ' runs in families,' its propagation is sometimes due 

 to maternal or other infection ; that environmental 

 conditions, such as the nature of the soil, seriously 

 affect its frequency ; that, with care in regard to 

 climate, surroundings, diet, exercise, &c., even 

 children with a consumptive tendency may rejoin 

 the healthy stock. None the less is it inadvisable 

 that consumptives should be parents, least of all 

 along with other consumptives. Allowing, again, 

 for the undeniable influences of early nutrition, 

 upbringing, and surroundings, all authorities admit 

 that dipsomania or its results tend to be trans- 

 mitted, often with the final consequence of ex- 

 tinguishing the family. Yet, in regard to the 

 inheritance of pathological conditions, it ought to 

 be noticed ( a ) that Virchow and others have hinted 

 at an 'optimism of pathology,' since some of the 

 less known abnormal variations may be associated 

 with new beginnings not without promise of pos- 

 sible utility; (6) that, by the intercrossing of a 

 tainted and a relatively pure stock, a recuperative 

 or counteractive influence may act so as to produce 

 comparatively healthy offspring, thus illustrating 

 what may be called the ' forgiveness of nature.' 



Social Inheritance. The widest problems of 

 heredity are raised when we substitute ' frater- 

 nities' 'for individuals, or make the transition to 

 social inheritance. For lack of reliable statist ic-, 

 and experts capable of wielding the statistical 

 method, the complex problems of the relation 

 between successive generations of a society have 

 rarely been essayed. The most important pioneering 

 is that of Galton, whose unique papers nave been 

 recently summed up in his Natural Inheritance 



