HEREDITARY TRANSMISSION 67 



That character which is common to these two distinct 

 processes is this, that, whether we consider the reproduc- 

 tion, or perpetuation, or modification of organic beings as 

 they take place asexually, or as they* may take place 

 sexually, in either case, I say, the offspring has a constant 

 tendency to assume, speaking generally, the character of 

 the parent. As I said just now, if you take a slip of a 

 plant, and tend it with care, it will eventually grow up and 

 develop into a plant like that from which it had sprung ; 

 and this tendency is so strong that, as gardeners know, 

 this mode of multiplying by means of cuttings is the only 

 secure mode of propagating very many varieties of plants ; 

 the peculiarity of the primitive stock seems to be better 

 preserved if you propagate it by means of a slip than if 

 you resort to the sexual mode. 



Again, in experiments upon the lower animals, such as 

 the polype, to which I have referred, it is most extra- 

 ordinary that, although cut up into various pieces, each 

 particular piece will grow up into the form of the primitive 

 stock ; the head, if separated, will reproduce the body and 

 the tail ; and if you cut off the tail, you will find that that 

 will reproduce the body and all the rest of the members, 

 without in any way deviating from the plan of the organism 

 from which these portions have been detached. And so 

 far does this go, that some experimentalists have carefully 

 examined the lower orders of animals, among them the 

 Abbe Spallanzani, who made a number of experiments 

 upon snails and salamanders, and have found that they 

 might mutilate them to an incredible extent ; that you 

 might cut off the jaw or the greater part of the head, or 

 the leg or the tail, and repeat the experiment several times, 

 perhaps, cutting off the same member again and again ; 

 and yet each of those types would be reproduced according 

 to the primitive type : nature making no mistake, never 

 putting on a fresh kind of leg, or head, or tail, but always 

 tending to repeat and to return to the primitive type. 



It is the same in sexual reproduction : it is a matter of 

 perfectly common experience, that the tendency on the 

 part of the offspring always is, speaking broadly, to re- 

 produce the form of the parents. The proverb has it that 

 the thistle does not bring forth grapes ; so, among our- 

 selves, there is always a likeness, more or less marked and 

 distinct, between children and their parents. That is a 

 matter of familiar and ordinary observation. We notice 



