136 THE PHENOMENON OF 



than to the Desmidiacese. While, in the Desmidiaceae 

 and Zygnemaceae, the last generation of vegetative cells 

 produces the seed-cells (spores) as a new generation, 

 since the latter shape themselves out free in the interior 

 of the conjugated parent-cells, through the loosening of 

 the contents of the latter from the walls, in Palmoglcea 

 the last vegetative generation passes directly into the 

 formation of seed-cells (spores), since the cells combining 

 in pairs by conjugation, enter into perfect union, i. e., 

 not merely mix their contents in a new structure, but 

 merge or flow one into another entirely (coat and con- 

 tents) like two drops of water. The large seed-cells 

 (spores) originating in this way gradually acquire a thick 

 coat and oily contents, passing into a summer-sleep, 

 overlasting the hot and dry season, till, with the recur- 

 rence of the cold damp season, the contents become 

 metamorphosed and divided, while the coat of the seed- 

 cell swells up and dissolves into jelly. Thus the primary 

 vegetative generation is produced as a new generation 

 out of the seed-cell, the contents first formed by blending, 

 dividing again, and becoming freed from the coat of the 

 mother-cell.* 



So far as we have hitherto examined the differentiation 

 connected with the succession of generations of the cells, 

 we have found solely like cells within each generation ; 

 we have seen, moreover, all the terminal links of the 

 multiplied series attain the conclusion of the cycle (as 

 fructification-cells) in the same way, accidental exceptions 

 being of course excluded. The further complications 

 arise not only from a greater difference presenting itself 

 in the successive generations, but from the cells of the 

 same generation also exhibiting different characters. 

 The latter, again, may happen in two ways : either two 

 daughter-cells originating in one and the same mother- 

 cell (therefore two sister-cells) are unlike each other, 

 or the daughter-cells of distinct mother-cells belonging to 



* Vide the figures in PI. 1, and the more minute description of Palmogleea 

 iu the Appendix. 



