THE IDADEQUACY OF THE CELL-THEORY. 119 



What is the difference between an organization embracing 

 one cell and one embracing two or many cells ? Certainly the 

 essential difference cannot lie in the number of cells. We must 

 look entirely behind the cellular structure for the basis of 

 organization. Even a highly differentiated organism may 

 reach a relatively late stage of development just as well without 

 cell-boundaries as with them, as we see so well illustrated in 

 the insect egg. If we fall back on the number of nuclei as the 

 essential thing, then we shall have to reckon with multinucleate 

 infusoria. In these forms do we not see that it is always the 

 same organism before us, as we follow its history through the 

 whole cycle of nuclear phases ? 



The essence of organization can no more lie in the number 

 of nuclei than in the number of cells. The structure which we 

 see in a cell-mosaic is something superadded to organization, 

 not itself the foundation of organization. Comparative embry- 

 ology reminds us at every turn that the organism dominates 

 cell-formation, using for the same purpose one, several, or many 

 cells, massing its material and directing its movements, and 

 shaping its organs, as if cells did not exist, or as if they existed 

 only in complete subordination to its will, if I may so speak. 



In the phenomena of regeneration and embryogenesis we 

 find abundant evidence. For the present I must limit myself 

 to a few features of development. 



Perhaps the peculiar formation of the embryo Toad-fish 

 (Batrachus) is as instructive a case as I am acquainted with. 



is quite unique, for it may become the receptacle of nuclei belonging originally 

 to other cells; in other words, /'/ becomes multiniicleate, not by t/ie multiplication 

 of its own nucleus, but by the acquisition of exotic nuclei. 



The acquired nuclei are what I have called elsewhere the "residual" nuclei, 

 which are left over when the formation of "infusoriform embryos" ceases. Each 

 of these nuclei enters into vital relations with the cell, and each undergoes the 

 differentiations characteristic of the true entodenn nucleus, so that in the end they 

 can only be distinguished by their positions. This seems to show that the differ- 

 entiation of nuclei may be controlled by the cell to which they are transplanted. 



One of Boveri's observations* shows that the same may be said of the chromo- 

 somes. One or more of the chromosomes, normally eliminated in the polar 

 globules, are sometimes carried into the cleavage-nucleus.. The supernumerary 

 chromosomes here undergo the regular transformations, quite unlike those which 

 they show when carried out in the polar globule. 



* Zellen-Studien. Heft 2, pp. 171 - 175. 



