314 Prof. M. Schultze on the Organization 



the cavity of the cell. The protoplasm is the most important 

 substance of the cell ; in it the functions of the latter are con- 

 centrated; in it exclusively are manifested all the chemical and 

 morphological changes which characterize the various phases of 

 cell-life. At the same time, inasmuch as it can produce on and 

 from its surface membranous and other matters of many kinds, 

 protoplasm is apparently quite exclusively the tissue-forming 

 substance. Protoplasm is also contractile. 



It is only by such suppositions that the movements in the 

 interior of cells (for example, the well-known cells of Tra- 

 descantia, and, I believe, even of the Char(e) can be explained. 

 The nature of the movement, the stream of granules, the ana- 

 stomosis of the threads (when a net of protoplasm-fibres exists in 

 the cell), all are in favour of the belief that the origin of the 

 movement lies in the protoplasm itself, and not exterior to it. 

 It is only by the assumption of a contractility of the protoplasm 

 that the changes of form of individual cells, the Amoeba-lW^e 

 movements of the Gregarina, of the lymph-corpuscles in the 

 blood, of individual ligament-cells, of the cells in the hearts of 

 embryos, &c., can be understood. 



With this contractility of the protoplasm, changes of form of 

 entire cells are, of course, hindered, or rendered quite impossible, 

 by the presence of a rigid membrane. But the less perfectly the 

 surface of the protoplasm is solidified into a membrane — the 

 nearer the cell remains to its original membraneless condition, in 

 which it only forms a naked mass of protoplasm with a nucleus, 

 the more freely and unobstructedly can the movements be mani- 

 fested. If such a cell be an independent organism, the protean 

 changes of form — the variation of the external form caused by the 

 contractility of the mass of protoplasm — manifest themselves 

 to us most strikingly. Thus we come to the Amoebce, of which 

 the unicellular nature is at least very probable, as transitions 

 to the GregarincE may be traced. It has been attempted to 

 adduce the contractile vesicle as an obstacle to this view, and 

 to the explanation of the AmoebcB as unicellular organisms. I 

 cannot see in this an essential obstacle ; for if protoplasm be 

 contractile, as can hardly now be doubted, the possibility of the 

 formation of a specially contractile space (a cavity contracting 

 rhythmically) is given*. 



* With this view we may very well bring into connexion the fact that 

 there are Amabce which receive nourishment only at a determinate spot on 

 the body. The cortical layer of the protoplasm need only condense a little, 

 in its tendency to the formation of membrane ; and the reception of foreign 

 bodies, in external juxtaposition, into the interior will at once take place with 

 less facility. But if, as in such cases will happen, one spot in the cortical 

 layer of the protoplasm remains in its original soft state, this becomes the 

 " mouth." Nay, it may come to the formation of a firm membrane, and 



