THE FORMATION OF GERM-CELLS 203 



confine myself to calling attention to the fact that even if a uni- 

 versal reproductive power existed in protoplasm, it certainlv 

 would not explain matters, /v^r this power is just what has to 

 be explained. 



If we know, for instance, that Infusoria are able to replace 

 great losses of substance, — so that when the oral region is cut 

 off, it, together with all the cilia and other minute structures, can 

 be formed anew, — a proof is thereby obtained that these uni- 

 cellular organisms actually possess the universal reproductive 

 power which Vines wishes to ascribe to vegetable protoplasm. 

 But does this help us in the slightest degree to understand the 

 fact, or to explain why the ultimate particles of the cell-body 

 become rearranged and transformed after a loss of substance 

 has occurred, just as is necessary for the reappearance of the 

 species ? Do we thereby gain the faintest idea as to how and 

 why the residual particles of the cell-body are compelled to give 

 up their previous form and connection, and to reconstruct 

 exactly that part which is required in order to render the whole 

 complete ? The assumption of a * reproductive power ' simply 

 amounts to the statement of the fact that regeneration occurs ; 

 and this, it seems to me, is equivalent to saying that the 

 reproductive power is a fundamental property of vegetable 

 protoplasm. 



In the case of the unicellular Infusorian we can. however, 

 hardly venture at present to attempt an explanation of this 

 problem, as we know very little of the vital units of which the 

 cell-body is composed, and of the forces situated within them. 

 But the case is different with regard to those organisms which 

 consist of many physiologically differentiated cells : in these we 

 are at any rate acquainted with the form and function of one 

 arrangement of the vital units of which the whole aggregate is 

 composed, and so we can attempt to deduce the functions of 

 the whole body from those of the units, and conversely to refer 

 the latter processes to a distribution of the forces amongst the 

 units composing the whole. We need not therefore confine 

 ourselves to the mere statement of the fact that a process 

 occurs by means of which the whole is completed, but we may 

 further inquire as to when this occurs, from what elements it 

 proceeds, how the whole body arises at all, and how so complex 

 a structure can be formed from the apparently simple substance 

 of the germ. 



