664 Blackman.—The Primitive Algae 
zoospore-formation and vegetative cell-division are one and 
indistinguishably the same thing. 
The cytological processes had been but little investigated 
till Dangeard (’ 99 ) contributed a long paper dealing with 
these in the Chlamydomonads and with the behaviour of the 
nucleus in division and in sexual fusion. This constituted 
a very distinct advance in our knowledge. 
One of the points investigated is the relation between the 
protoplasm of the chloroplast and that of the rest of the cell 
in those types which are only just removed by evolution 
from colourless Flagellates. Chlorogonium euchlorum has 
the characters of a transitional form, and the earliest writers 
held the chlorophyll to be diffused through the cytoplasm 
generally, but Franck (’ 97 ) described differentiated discoid 
chloroplasts or a few spiral bands round the cell. Dangeard 
shows by skilful staining that there is but one chloroplast, 
as in the rest of the family, but that this is perforated with 
masses and strands of the central colourless protoplasm so 
that it may appear cut up into bands or disks. 
Chlorogonium euchlorum seems to be very variable and 
erratic in its cell-characters, for the pyrenoids may vary from 
four to thirty-two, contractile vacuoles may be present in 
large numbers, and finally the individuals from one special 
habitat really seemed to have diffuse chlorophyll, colouring 
all the cell except a fragment at each end. The author is 
unable to suggest the cause and significance of these variations 
in one species of a family otherwise characterized by the 
constancy of its specific cytological characters. 
The structure of the nucleus in the Chlamydomonads can 
be very clearly made out and all stages of karyokinetic division 
followed, and the chromosomes counted. The number for 
each species (10-30) is fairly constant. 
Non-karyokinetic division of the nucleus was observed 
only in Chlorogonium , and this quite exceptionally. As this 
is generally held to signify degeneration, the author thinks it 
probably a prelude to death or sexual reproduction in this case. 
