Algae and the Principles of their Evolution, i i i 
Hariotina , and as intermediate forms the different species of 
Coelastrum. 
It may be imagined that Coelastrum sphaericum , for 
example, has been derived from a lower form of the Proto- 
coccoideae with autospores. As in the former series, the 
spores may be at the time of their expulsion either free or 
united together by intermediate mucilaginous matter. In 
such a theoretical type the autospores would have been 
grouped in a globular colony. This may often be observed 
in some very doubtful species, such as the so-called Chloro- 
coccum infusiomim , Pleurococcus angulostts , &c., described by 
Artari 1 . 
One of the causes of the production of auto-colonies, 
in this and in other cases, is the rapid multiplication of 
the nuclei. At a very early stage of their development 
after their extrusion, the cells of the Pediastreae contain 
several nuclei (4-32-64). By direct heredity each of the cells 
assumes within the mother-cell the shape of the parent, and 
when the mother-cell is provided with sculptures or prolonga- 
tions, as is the case in some species of Coelastimm and in 
Hariotina , these appendages are already formed at the instant 
of the extrusion of the new colony. 
This theory of the evolution of the group may be demon- 
strated by the very specific variations of the different species 
of Coelastrum , for example C. sphaericum 2 . In the ordinary 
condition the cells of the coenobium of this species remain 
united together at the time of the birth of the young colonies. 
The cells of the parent colony are for the most part emptied 
of their contents ; in other cases each of the cells of the 
coenobium is separated, and can produce a new colony in this 
condition of desaggregation, or else may give birth to a two- 
celled body (as occurs in Sorastrum) in the cells of which new 
colonies are formed. Lastly, gelatinous unicellular or multi- 
cellular conditions are possible. 
1 Untersuchungen iiber Entwicklung und Systematik einiger Protococcoideen, 
Bulletin de la Societe Imp. des Naturalistes de Moscou, No. 2, 1892, p. 29. 
2 Chodat, Sur l’JEvolution de Coelastrum, Bull. Herb. Boissier, 1896, p. 273. 
