ALGOLOGICAL NOTES 323 



sudden attack of immense numbers of a minute Chytridiaceous 

 fungus, which completed destroyed the CEclogonium filaments, the 

 young plants, and the oospores, in rather less than two days. 



These observations are of some interest, as they assist in 

 elucidating the problem of the relationships between the macran- 

 drous and nannandrous species of CEdogonium. The macrandrous 

 species probably arose from the monoecious species by the physio- 

 logical differentiation of the zoogonidia, some of which gave rise 

 only to female filaments, and others only to male filaments. 

 There is thus a differentiation of the motile gonidia into androzoo- 

 gonidia and gynozoogonidia. In the nannandrous species there is 

 a further differentiation between these two types of zoogonidia in 

 point of view of size, the androzoogonidia being as a rule not 

 more than half the size of the gynozoogonidia, and intermediate 

 between the gynozoogonidium and the antherozoid. All these 

 motile bodies exhibit precisely similar morphological characters. 

 How have the androzoogonidia of the nannandrous species arisen ? 

 It is not at all probable that they have arisen from the anthero- 

 zoids of the monoecious species by an increase in the size of the 

 antherozoid mother-cells, because two antherozoids invarably arise 

 in each cell of the antheridium, by the division of the protoplast, 

 whereas the entire protoplast of the androzoogonidangium forms 

 a single androzoogonidium. Seeing that this is also the case in 

 the formation of both the androzoogonidia and gynozoogonidia of 

 the macrandrous species, and in the gynozoogonidia of the 

 nannandrous species, it is reasonable to suppose that the small 

 androzoogonidium of the latter has arisen merely by a reduction 

 in size, which has gone on hand in hand with a greater sexual 

 differentiation. The specialization has become such, that the 

 androzoogonidia are attracted to the vicinity of the oogonia, and 

 only germinate either on their walls or on the walls of the 

 supporting-cells. The male plant which is then developed is so 

 reduced that there is only one vegetative cell, or sometimes none, 

 and one antheridium consisting of from one to five cells. The 

 reduction of the male filaments to ** nannandria " is to be 

 correlated with the fact that the antherozoids are set free in the 

 immediate vicinity of the oogonia, and, therefore, fewer of them 

 are required in order to ensure fertilization. Moreover, vegetative 

 cells are unnecessary except as a support for the single antheri- 

 dium, and for which one cell easily suffices. 



In (E. fonticola the cells of the vegetative filaments (female ?) 

 are so short that it is scarcely possible in many cases to distin- 

 guish between gynozoogonidangia and androzoogonidangia, and 

 the dimensions of the plants developed from many of the zoogo- 

 nidia suggest that this species is one in which the full 

 differentiation in size between the androzoogonidia and gyno- 

 zoogonidia has not yet been attained. It may thus be an 

 CEdogonium intermediate, as regards its male filaments, between 

 the truly macrandrous and nannandrous types. 



The views expounded above as to the origin of the dwarf males 

 of the nannandrous species of CEdogonium, by the reduction and 



2 A 2 



