CELL-FORMATION. 131 



lated in the interior of the rest of the contents of the 

 parent-cell (Formation of free germ-cells in Algae, Lichens, 

 Fungi, and of the endosperm-cells of Phanerogamia.) 



2. The entire contents of one cell, or of two cells con- 

 nected by conjugation, unite into one free, globular, or 

 ellipsoidal mass (Formation of the germ-cells of Zygne- 

 macese). 



3. The entire contents of a cell divide into two or more 

 portions (parietal cell-formation in cell- division.) 



4. The entire contents of a short branch of a cell, or 

 of the terminal portion of a longer branch, separate from 

 the rest of the contents of the cell (parietal cell-formation 

 in the so-called constriction, as, for instance, in the for- 

 mation of the germ-cells of several Algae \Vancheria, &c.] 

 and many Fungi). 



The phenomena exhibited by the individualization of 

 the contents, in normal cell-formation, are externally the 

 same as in abnormal cell-formation. In abnormal cell- 

 formation, external, accidental influences exert a disturb- 

 ing action on the life of the cell. In normal cell-forma- 

 tion, the presence of a 'nucleus must be especially counted 

 among the conditioning causes. I have demonstrated it 

 to be in the highest degree probable that nuclei are always 

 present both in parietal and free normal cell-formation. 

 They are wanting in abnormal cell-formation, and in this 

 lies the essential distinction between normal and abnormal 

 cell-formation. 



If we may presuppose the necessity of the presence of 

 a nucleus in the normal individualization of portions of 

 contents, the processes must be completed in the follow- 

 ing ways, in the four forms of individualization just 

 mentioned : 



1 . One or more nuclei originate in the contents of the 

 cell. Each of these collects the contents in its immediate 

 vicinity upon its surface. These portions of contents are 

 composed of homogeneous mucilage, or mucilage with 

 which is intermingled other assimilated substances, such 

 as chlorophyll or other colouring matters, starch, oil, &c. 



