659 
and the Flagellata. 
Chi. Kleinii. He cultivated this under various different con¬ 
ditions, and found that its well-marked cytological characters 
remained quite constant. This species is further of interest 
because it shows less of the characteristic motility in its vege¬ 
tative condition than any other member of the Volvocineae. 
It only swims freely for a very short time, never dividing while 
free, and then comes to rest on some substratum, and surrounds 
itself with a mucilaginous excretion, which may leave the cilia 
still projecting or may include them. In this condition, by 
repeated transverse bipartition, large but very loosely coherent 
aggregates of individuals are formed, each within its own 
mucilaginous envelope. 
Some such resting Palmella-like condition occurs as a phase 
in the life-history of all the Chlamydomonas species, but in 
this form it is the preponderating condition, and brings us 
very close to the types found in the Tetrasporaceae, which are 
all non-motile throughout their vegetative condition. 
Dill, in 1895, published a most important paper which 
proved the constancy of the cytological specific characters 
for a large number of species of Chlamydomonas. At Kleb’s 
suggestion Dill cultivated all the species he could collect, in 
Knop’s solution of various strength, in water, in sugar solution, 
and on damp moss. He found that variations might thus be 
produced in the size of the individuals and in the thickness 
of their cell-walls, but that the cytological characteristics 
given above remain unchanged ; with this solitary exception, 
that with ChL longistigma nutritive salt solution causes- 
elongation and frequently bipartition of the pyrenoids, so that 
four are present in place of the normal two. 
Six of the species Dill cultivated were newly discovered 
by himself, which brought the number of well-established 
species up to fifteen, all of which can be recognized in their 
vegetative condition. This is a very remarkable result when 
we consider that with higher genera of Algae, Spirogyra , 
Oedogonium and other filamentous forms rich in species, it is 
only from the reproductive organs that the species can be 
certainly diagnosed. 
