348 THE CELL 



water, it develops root-forming cells at its lower extremity: thus 

 the cells are here executing functions, very different from their 

 original ones, which proves that they possessed this capacity 

 potentially. Further, on the other hand, shoots can develop from 

 severed roots, and even subsequently can produce male and female 

 sexual products. In this case, therefore, sexual cells proceed 

 directly from the component parts of a root-cell, and hence serve 

 for the reproduction of the whole. Certain hydroid polyps, 

 according to von Loeb (IX. 17), display similar powers. 



Most botanists agree with the theory, recently advanced by de 

 Vries (IX. 30), in opposition to Weismann, which states that all, 

 or at any rate by far the greater number, of the cells of a vegetable 

 body contain all the hereditary attributes of their species in a 

 latent condition. The same is true of the lower animal organisms, 

 although we are unable to prove it for the higher ones. However, 

 on this account, it is not necessary to conclude that the cells of 

 the higher and lower organisms differ so much from one another, 

 that the latter possess all the attributes in a latent condition, 

 and therefore the whole hereditary mass, whilst the former only 

 contain a part of it. For it is quite as likely that the incapacity 

 of most of the cells of the higher animals to develop latent 

 properties, is due to their external conditions, which have produced 

 a great differentiation of the cell-body, in which the hereditary 

 mass is enveloped, or to other similar conditions. 



Johannes Miiller (IX. 18), has raised the question: "How does 

 it happen, that certain of the cells of the organised body, although 

 they resemble both other cells and the original germ-cell, can 

 produce nothing but their like, i.e. cells which are capable of 

 developing into the complete organism ? Thus epidermal cells 

 can only, by absorbing material, develop new epidermal cells, 

 and cartilage cells only other cartilage cells, but never embryos 

 or buds." To which he has made answer: "This may be due to 

 the fact, that these cells, even if they possess the power of 

 forming the whole, have, by means of a peculiar metamorphosis 

 of their substance, become so specialised, that they have entirely 

 lost their germinal properties, as regards the whole organism, and 

 when they become separated from the whole, are unable to lead 

 an independent existence." 



Whatever opinion is held as regards the conditions present in 

 the higher animal, it is quite sufficient for our purpose to acknow- 

 ledge, that in the plants and lower animals, all the cells which are 



