NOTES AND MEMORANDA. 181 



to which, probably, the author's Obelidium also should be 

 referred. Rhizidium and Polyphagus agree in the mode of 

 the germination of the resting-spores, the whole contents in 

 each coming forth and becoming a zoosporangium. In this 

 respect, too, they call to mind Sorokin's Zygochytrium and 

 Tetrachytrium. In the last-mentioned organism; however, 

 the zoosporangium is formed by the emerged protoplasm only 

 after complete separation from the prosporangium, whilst in 

 Polyphagus the zoosporangium remains always attached to 

 the prosporangium, as already described. In this regard, the 

 mode of development of the zoosporangium in Polyphagus, 

 Zygochytrium, and Tetrachytrium, corresponds to the ana- 

 logous phenomena shown by the Saprolegniaceous genus 

 Pythium, whilst in their sexual development they approach 

 not less to the Zygomycetse, most marked in Zygochytrium. 

 In Polyphagus, however, there is a distinction of the sexes 

 presented, characterising the individuals as dioicous, and a 

 new remarkable stage intervening between conjugation and 

 sexual fertilisation is here brought to notice. 



Cylindrocapsa involuta, Reinsch. 



The alga first discovered by Reinsch,^ and named as above, 

 is amongst the rarest of freshwater algae, and curiously 

 enough it is that in it Cienkowski^ has lately discovered a 

 sexual development. 



The alga consists of unlranched confervoid filaments, the 

 joints in single series and mostly presenting distinctly lami- 

 nated walls. Like other similar forms they are collectively 

 enclosed in a common sheath, but here this is very thick and 

 distinctly laminated. According to the more or less vigorous 

 growth their chlorophyllaceous cells are variously figured ; in 

 actively growing examples the middle of the cell is occupied 

 by a rather large amylaceous granule, around which smaller 

 ones are disposed ; in those less vigorously growing they are 

 densely full of such granules. Young filaments are attached 

 to foreign objects by a colourless basis, but older they are met 

 with free. The upper end of the alga is closed and bluntly 

 rounded. 



According to the author's observations, however, this typical 

 habit may be altered in various ways. The envelopes of the 

 cells may become more gelatinous and cell-division ensue in 



' P. F. Reinsch : ' Die Algenflora des mittleren Theiles von Frauken,' 

 p. 66, t. vi, f. 1, 2. 



^ Cienkowski : " Zur Morphologic der XJlothricheen," in ' Melanges Bio- 

 logiques tires du Bulletin de I'Academie Imperiale des Sciences de St. Peters- 

 bourg,' t. ix, p. 531. 



