343 
Nemalion multifidum , Ag. 
nuclei do not become completely organized. The chromatic material is 
gathered together into nucleoli, but no nuclear membranes are formed and 
the two bodies lie side by side for some time before they finally disinte- 
grate (Figs. 85-7). The appearance of these two bodies side by side is 
a very common one, and it is probable that this division takes place 
frequently. There is a considerable variation as to the time at which it 
occurs. It may take place very soon after the cyst has been cut off 
(Figs. 85, 86), or it may not occur until the filament is two-celled (Fig. 83). 
The presence of this division is very interesting since it recalls the second 
division of reduction mitoses, as reported in the germination of certain algal 
spores (e. g. Spirogyrd) ; but the evidence is clear that this is not the point 
of reduction in Nemalion , and the mitosis may simply refer to a time when 
the basal cell of the sporeling retained vegetative activity, perhaps giving 
rise to additional filaments. 
Meanwhile the germ tube has grown greatly in length and the tube 
nucleus has come to occupy a position lateral to the now quite long 
chromatophore (Fig. 89). Usually the chromatophore divides first 
(Figs. 8 1, 90), followed by the nucleus, but the reverse may be the case 
(Figs. 89, 92). The second mitosis varies in no particular from the first. 
After nuclear division a cross-wall is laid down, resulting in a two-celled 
filament. In the same manner the third mitosis takes place and the third 
cell is formed (Fig. 94). Miss Chester (1898) has followed the development 
of the sporeling through subsequent phases, until it assumes the appearance 
and method of growth of the typical Nemalion plant. 
The events recorded in this paper seem clearly to indicate that there is 
no phase in the life-history of Nemalioyi corresponding to the sporophyte 
of other groups. The cystocarp is shown not to be fundamentally sporo- 
phytic in nature, but to correspond closely to the tissue development 
leading to zoospore formation in the fertilized oogonium of Coleochaete , 
where Allen (1905) has placed for this plant the point of chromosome 
reduction in the first mitosis of the fertilized egg. 
Discussion. 
The problem of alternation of generations in the red algae is a per- 
plexing one, and would demand more space for a complete discussion than 
can here be given. It will, therefore, be but briefly considered. 
We find in the Florideae two distinct divisions. The first group, 
termed £ haplobiontic ’ by Svedelius (1915) and represented by Nemalion 
and Scinaia , presents a life-history without a change of chromosome 
number in the cystocarp and without a tetrasporic phase. The second group, 
termed ‘ diplobiontic ’, carries a diploid number of chromosomes through 
the gonimoblasts of the cystocarp, through the carpospore, and through 
