HEREDITARY TRANSMISSION 65 



classed as belonging to any sex at all. In the second case, 

 it is in consequence of the mutual action and interaction of 

 certain portions of the organisms of usually two distinct 

 individuals, the male and the female. The cases of 

 asexual perpetuation are by no means so common as the 

 cases of sexual perpetuation ; and they are by no means so 

 common in the animal as in the vegetable world. You are 

 all probably familiar with the fact, as a matter of experience, 

 that you can propagate plants by means of what are 

 called " cuttings ; " for example, that by taking a cutting 

 from a geranium plant, and rearing it properly, by supplying 

 it with light and warmth and nourishment from the earth, 

 it grows up and takes the form of its parent, having all the 

 properties and peculiarities of the original plant. 



Sometimes this process, which the gardener performs 

 artificially, takes place naturally ; that is to say, a little 

 bulb, or portion of the plant, detaches itself, drops off, and 

 becomes capable of growing as a separate thing. That is 

 the case with many bulbous plants, which throw off in 

 this way secondary bulbs, which are lodged in the ground 

 and become developed into plants. This is an asexual 

 process, and from it results the repetition or reproduction 

 of the form of the original being from which the bulb 

 proceeds. 



Among animals the same thing takes place. Among the 

 lower forms of animal life, the infusorial animalculse we have 

 already spoken of throw off certain portions, or break 

 themselves up in various directions, sometimes transversely 

 or sometimes longitudinally ; or they may give off buds, 

 which detach themselves and develop into their proper 

 forms. There is the common fresh-water Polype, for 

 instance, which multiplies itself in this way. Just in the 

 same way as the gardener is able to multiply and reproduce 

 the peculiarities and characters of particular plants by 

 means of cuttings, so can the physiological experimentalist, 

 as was shown by the Abbe Trembley many years ago, 

 so can he do the same thing with many of the lower forms 

 of animal life. M. de Trembley showed that you could 

 take a polype and cut it into two, or four, or many pieces, 

 mutilating it in all directions, and the pieces would still 

 grow up and reproduce completely the original form of 

 the animal. These are all cases of asexual multiplication, 

 and there are other instances, and still more extraordinary 

 ones, if\ which this process takes place naturally, in a more 

 66 c 



