59 



tetrasporic cell from its inception, pjid in one ca.se, at 

 least, t\/o nuclei have been noted in t}ie very young tet- 

 raspoi'e mother cell. Thir. recalls tlie suggestion of KEY- 

 DRICH ('02) of a possible sexual significance of the tet- 

 raspore. Exainination of a large series of developing tet- 

 raspore mother cells convinces me, hov;ever, thcit there Is 

 here a purely accidental phenomenon, v;hich has no place in 

 the normal life history, s.nd which is not to be considered 

 as analogous in any way to the se:Kual process. 



The cells of the tetrasporic branch appear at? first 

 not to secrete cellvxlose v;^llls of their own. The stalk 

 cell, with its tetraspore mother cells, remains siirroionded 

 by the gela.tini7,ed wall of the vegetative cell on which it 

 is borne. Thiff. wall, much swollen, covers the tetra,sporic 

 branch completely (fig, 115). It continues to swell and 

 by the time the spores are ready to be discharged it seems 

 to dissolve lejr'gely or completelj'' in the sea-wa.ter. 



The stalk cell increa,ses in size, and its nucleus at 

 tlie same time divides b;'- successive mitoses until usually 

 16 da,ughter nuclei are finally produced. V.'ith tlie grov;th 

 of tiie cell ir size, tlie cytoplasm becomes less dense, and 

 vacuoles appear iii it. There may be a single large central 

 vacuole (fig. 115), or several sins.ller ones variously dis- 



