AS THE ELEMENTAL GERM OF AN ORGANISM 357 



cella?, which are more similar to one another than those of the nu- 

 cleus. For, firstly, fragments of a cell, which contain the nucleus, 

 are capable of normal development (vide experiments, p. 330). 

 Secondly, the first division plane can be induced, by means of ex- 

 ternal influences, to divide the contents of the eg-or in the most 

 various directions, without causing any deviation from the normal, 

 in the product of development. Thirdly, considerable changes of 

 position of the egg substance may be induced, by means of gravity, 

 in Frog's ova which have been forced into an abnormal position, 

 without causing any difference in their subsequent development. 

 Fourthly, we are able to infer, that the micella? are loosely con- 

 nected together from the streaming movements of protoplasm, in 

 which, of necessity, the groups of micellae are obliged to push past 

 one another in the most different directions, and apparently with- 

 out any method. On the other hand the complicated phenomena 

 of the whole process of nuclear segmentation indicate a more 

 stable arrangement of the nuclear substance. 



Nageli has assumed that there is a similar difference between 

 his hypothetical trophoplasm and idioplasm. He states (pp. 27, 

 41) : " If the arrangement of the micella? determines the specific 

 properties of the idioplasm, the latter must be composed of a fairly 

 solid substance, in order that the micella? may not be displaced in 

 consequence of active forces in the living organism, and in order 

 to secure to the new micella?, which become deposited during multi- 

 plication, a definite arrangement. On the other hand, ordinary 

 plasma consists of a mixture of two kinds, fluid and solid, the two 

 modifications easily merging into one another, whilst the micella?, 

 or groups of micella? of the insoluble form, are more easily able to 

 push past one another, as must be assumed to be the case when 

 the streaming movements occur." Nageli, therefore, makes the 

 assumption, which however cannot be proved off-hand, that the 

 idioplasm is spread out like a connected net throughout the whole 

 organism. 



IV. Development of the Elemental Germs. Having 

 assumed that there is a special germ substance or idioplasm in the 

 cell, we must next enquire how the individual idioblasts become 

 active, and thus determine the specific properties or the character 

 of the cell as a result of their development. 



It has been suggested, that during the process of development 

 of the ovum, the idioplasm is qualitatively divided unequally by 



