552 ON HEREDITY. 



wliicb the same cow may liave when their sires have been of the short- 

 liorned blood, may, in addition to slioit-horu characters, have others 

 which are not short-horned but highhind. 



The most noteworthy instance of this transmission of characters ac- 

 quired from one sire througli tlie same mother to her offspring by other 

 sires, is that given in the often-quoted experiment by a former Lord 

 Morton.* An Arabian mare in his possession produced a hybrid, the 

 sire of which was a quagga, and the young one was marked by zebra- 

 like stripes. But the same Arabian had subsequently two foals, the 

 sire (if which was an Arab horse, and these also showed some zebra-like 

 markings. How then did these markings characteristic of a very differ- 

 ent animal arise in these foals, both parents of which were Arabians? 

 1 can imagine it being said that this was a case of reversion to a very 

 remote striped ancestor, common alike to the horse and the quagga. 

 But to my mind no such far-fetched and hypothetical explanation is 

 necessaiy. The cause of the appearance of the stripes seems to me to 

 be much nearer and more obvious. I believe that the mother had ac- 

 quired during her prolonged gestation with the hybrid, the power of 

 transmitting quagga-like characters from it, owing to the 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 pla 

 cental mammals an interchange of material takes place in opposite di- 

 rections, from the young to the mother as well as from the mother to 

 the young, t In this way, the germ-plasm of the mother, belonging to 

 ova which had not yet matured, had become modified whilst still lodged 

 in the ovary. This acquired modification had influenced her future 

 offspring, derived from that germ-plasm, so that they in their turn, 

 though in a more diluted form, exhibited zebra-like markings. If this 

 explanation be correct, then we have an illustration of the germ-plasm 

 having been directly influenced by the soma, and of somatogenic ac- 

 (juired characters having been transmitted. 



Those who uphold the view that characters acquired by the soma 

 can not be transmitted from parents to offspring undoubtedly draw so 

 large a check on the bank of hypothesis that one finds it difficult, if not 

 impossible, to honor it. Let us consider for a moment all that is in- 

 volved in the acceptance of this theory, and apply it in the first instance 

 to man. On the supposition that all mankind have been derived from 

 <;ommon ancestors through the continuit}" of the germ-plasm, and that 

 this ])lasm has undergone no modification from the j)^r,vo«<f or soma of 

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

 would follow that the primordial human germ-i)lasm must have con- 

 tained within itself an extraordinary potentiality of development; a 



* Philosophical Transactions, 1881 ; also DATwin's Animals and Plants nder Domestica- 

 tion, 1st ed., 1S68, vol. i, p. 40:^. 



t See for facts and experimeuts Ensaijs by Professors Harvey aud Gusserow and Mr. 

 Savory; also my Lectures on the Comparative Anatomy of the Placenta, Edinburgh, 1876, 



