TRANSACTIONS OF SECTION II. 709 



nearer and move obvious. I believe that tlie mother liad acquired durinsf lier 

 prolonged gestation witli the hybrid, the ])ower of transmitting rjuagga-like charac- 

 ters from it, owing to tiie interchange of material which had taken place between 

 them in connection with the nutrition of the young one. For it must be kept in 

 mind that in placental mammals an intercliange of material take.^ place in opposite 

 directions, from the young to the mother as well as from the mother to the young.' 

 In this way the germ-pla^m of the mother, belonging to ova whicli had not yet 

 matured, had become modified whilst still lodged in the ovarv. Tiiis acquired 

 modification had influenced her future oll'siiring, derived from that germ-plasm, so 

 that they in their turn, though in a more diluted form, exhibited zebra-like mark- 

 ings. If this explanation be correct, then we have an illustration of the germ- 

 plaam having been directly influenced by the soma, and of somatogenic acquired 

 characters having been transmitted. 



But there are other facts to show that the isolation of the germ-cells or "'erm- 

 plasm from the soma cells is not so universal as might at the first glance be supposed. 

 Weismann himself admits that in the Ilydroids the germ-plasm is present in a verv 

 finely divided, and therefore invisible, state in certain somatic cells in the beginning 

 of embryonic development, and that it is then transmitted through innumerable 

 cell generations to those remote individuals of the colony in which sexual products 

 are formed. The eminent botanist Professor Sachs states that in the true mosses 

 almost any of the cells of the roots, leaves, and shoot axes may form new shoots and 

 give rise to independent living plants. Plants which produce flowers and fruit may 

 also be raised from the leaves of the Begonta. I may also refer to what is more or less 

 familiar to everybody, that the tuber of the potato can give rise to a plant which 

 bears flowers and fruit. Now in these cases the germ-plasm is not collected in a 

 definite receptacle isolated from the soma, but is dift'used through the cells of the 

 leaves of the Begonia or amidst those of the tuber of the potato, and the propaga- 

 tion of the potato may take place through the tuber for several generations without 

 the necessity of having to recur to the fruit for seed. It seems ditlicult, therefore, 

 to understaiid why, in such cases, the nutritive processes which afl'ect and modify the 

 soma cells should not also react upon the germ-plasm, which, as Weismann admits, 

 is so intimately associated with them. 



Those who uphold the view that characters acquired by the soma cannot be 

 transmitted from parents to oftspring undoubtedly draw so large a cheque on the 

 bank of hypothesis that one finds it difficult, if not impossible, to honour it. 

 Let us consider for one moment all that is involved in the acceptance of this 

 theory, and apply it in the first instance to Man. On the supposition that all man- 

 kind have been derived from common ancestors through the continuity of the germ- 

 plasm, and that this plasm has undergone no modification from the persona or 

 «oma of the succession of individuals through whom it has been transmitted, 

 it would follow that the primordial human germ-plasm must have contained 

 within itself an extraordinary potentiality of development — a potentiahty so varied 

 that all the multiform variations in physical structure, tendency to disease, 

 temperament, and other characters and dispositions which have been exhibited by 

 all the races and varieties of men who either now inhabit or at any period in the 

 world's history have inhabited the earth, must have been included in it. But if 

 we are to accept the theory of Natural Selection, as giving a valid explanation of 

 the origin of new species, then the non-transmissibility of somatogenic acquired 

 characters has a much more far-reaching significance. For if all the organisms, 

 whether vegetable, animal, or human, which have lived upon the earth have arisen 

 by a more or less continuous process of evolution from one or even several siui])le 

 cellular organisms, it will follow as a logical necessity of the theory of the non- 

 transmission of acquired characters, that these simple organisms mu.«t have con- 

 tained in their molecular constitution a potentiality of evolution into higher and 

 more complex forms of life, through the production of variations, without the inter- 



' See, for facts and experiments, Essays, by Professors llar\ey and Gusserow and 

 Mr. Savory; also my Lectures on the Comjmratire Anatomy of the Placenta, Edin- 

 bnrgli, 187G. 



1S80. 3 D 



