140 VEGETABLE CELLS. 



case, that the primary nucleus does not become dissolved, 

 bat that it is this which becomes divided. 



4. Four nuclei are produced, probably by the division 

 of the primary central nucleus into two, each of which 

 becomes again divided. The four nuclei assume a tetra- 

 hedral arrangement. The contents separate into four por- 

 tions, each of which contains one of those nuclei in its 

 centre. The parent-cell divides by parietal cell-formation 

 into four tetraJtedr ally -arranged secondary cells. I have 

 hitherto only observed this process in the new single- 

 celled genus of Algae Tetrachococcus* 



5. The lateral (primary] nucleus of the parent-cell be- 

 comes absorbed. A new secondary nucleus makes its ap- 

 pearance in the centre of the parent-cell. At its sides 

 originate two smaller nuclei. 



A. The secondary nucleus of the parent-cell becomes ab- 

 sorbed. The contents separate into two portions, each of 

 which contains one of those smaller nuclei in the middle. 

 The parent-cell divides by parietal cell-formation into two 

 cells with central nuclei. Each of the two nuclei divides 

 into two nuclei, and each of the two cells divides again 

 into two secondary cells by parietal cell-formation. 



B. The two small nuclei divide, so that now four still 

 smaller nuclei lie around the large secondary nucleus in 

 the parent-cell. 



a. The secondary nucleus of the parent-cell becomes 

 absorbed. The four small nuclei assume a tetrahedral ar- 

 rangement. The contents separate into four portions, each 

 having one of these four nuclei in the centre. The parent- 

 cell divides by parietal cell-formation, into four tetrahe- 

 dr ally -arranged cells with central nuclei. 



b. Some, or all of the four small nuclei divide, so that 

 then from five to eight still smaller nuclei lie around the 

 large central secondary nucleus of the parent-cell. The 

 latter becomes absorbed. The contents separate into just 



JL J 



as many portions as there have been small nuclei produced, 



* Nageli, Neuern Algensysteme. Zurich, 1 847. 



