OiV THE NATURE OF CELL-ORGANIZATION. 93 



If, therefore, I omit from consideration the chromatophore 

 and the centrosome in the following, it is because the former 

 has been fully treated by able botanists, and the latter is 

 not sufficiently known, to my knowledge, to admit of useful 

 discussion in connection with our subject. If, however, the 

 centrosome be shown to be an organ of the cell, contrary to 

 my former conclusion above alluded to, with a morphological 

 significance comparable to that of the nucleus or the cyto- 

 plasm, the inference I advance in regard to the nature of the 

 latter organs will apply equally well to the former. 



Confining our remarks, then, to the nucleus and the cyto- 

 plasm, we may first ask whether the nucleus is to be regarded 

 as an organ in a morphological sense, or only in a physiological 

 one. Are nucleus and cytoplasm products of differentiation 

 from some homogeneous aiilagc in the sense that all morpho- 

 logical organs are, or may not their constant occurrence in 

 the cell rather be regarded as the result of a union formed in 

 the remote past, between two organisms originally independent 

 and dissimilar — a union of such a kind that ages of mutual 

 adaptations have rendered their independent existence no longer 

 possible 1 Is it not possible to regard the cell as a symbiotic 

 community, in which the cytoplasm represents one group of 



originates in the inside of the nuclear membrane. Brauer's view, however, does 

 not militate against my statement that the centrosome is the cyto-microsome of a 

 gigantic size, and that wherever cytoplasmic net-work exists there is a possibility 

 of developing a microsome. When the centrosome originates inside of the 

 nuclear membrane, it may be said, for a descriptive purpose, that it is derived 

 from the nucleus; when it originates outside of the nuclear membrane, such 

 a centrosome may be said to be cytoplasmic in its origin. Such a distinction is 

 purely a nominal one, however, from my standpoint, and I believe the general 

 statement that all centrosomes are cytoplasmic in their origin is fundamentally a 

 correct one. Confusion only arises when we do not keep in mind the fact that 

 the cytoplasmic net-work, in the substance of -which the microsome and centrosome 

 arise, exists on both sides of the nuclear metnbrane, and the strnctin-e known as 

 nucleus, contains a great deal of cytoplasmic substance in it. 



As is beautifully shown in Brauer's more recent paper (Zjtr Kcuutniss dcr Sper- 

 matogenese von Ascaris tnegalocephala. Arch. f. mikr. Anat., Bd. 42, 1893, August, 

 p. 185), the fact that in one variety of Ascaris inegalocephala, namely, univalens, 

 the centrosome lies inside, and in another variety, bivalens, outside of the nuclear 

 membrane, is enough, to my mind, to show that it is the substance which gives 

 rise to the centrosome, and not the position where the centrosome makes its first 

 appearance, which we must consider in the determination of its homology. 



