330 BOTANICAL GAZETTE [APRIL 
and Protopsis includé in part previously described species, and Gyrodinium 
replaces SHUtT?’s genus Spirodinium which is ae zoolog cong e 
other new genera are established to contain newly discovered species 
A few minor sl gota sae errors Occur, putt in general the work is 5 reanmeles 
ably freefromthem. The figures ly distributed and frequently 
many pages from the cate to them. It would greatly facilitate the use 
of the book if the references were by page instead of merely to the figure. 
These are trifling defects, however, in a work of such unusually permanent 
value. It is to be confidently expected that its publication will prove a distinct 
stimulus to further study in a field where there is still much to be learned.— 
G. W. Martin 
A new type of nuclear division.—CHATTON,?in a brief but significant paper 
throws new light on the peculiar nuclear phenomena in the Peridiniales de- 
scribed by LAUTERBORN, JOLLOS, BORGERT, and in his own earlier contribu- 
tions. His studies were made on species of Syndinium, which live parasitically 
in the body cavity of copepods, especially favorable material because of the 
small number of chromosomes. These have previously been described as ten 
somewhat curved filaments from a single pole like the ribs of an umbrella. Fur- 
ther study has shown that this structure is in reality composed of five v-shaped 
chromosomes with very sharp bends, with the points of the v’s converging at 
the pole. Cleavage takes place throughout the length of the chromosomes, 
so that ten V-shaped daughter chromosomes are formed. Five of these remain 
grouped about the original pole; the points of the remaining five become 
centered about a new pole which is at first close to the original one, then 
gradually moves away. In some species the cleavage is completed at once; 
in others the daughter chromosomes remain united at their tips and turn as 
upon a hinge, so that a bipolar spindle-shaped structure (not a true achromatic 
spindle) is formed, composed of the two series of v-shaped chromosomes 
converging at either end. The chromosomes then break apart, and it is this 
separation which was formerly interpreted as a transverse division of chromo- 
somes, when it is in reality merely the final separation of chromosomes pre- 
viously formed by longitudinal fission. Nothing resembling a true spindle 
was seen. 
Ordinarily no resting stage appears to occur, but it was observed in certain 
cases where the development of the peridine had been inhibited by some 
factor, as, for example, the presence of another parasite. In such cases the 
nucleus appeared to be composed of a large number of microsomes grouped 
around a central nucleolus. 
A division of this kind, while distinctly simpler than one taking place in 
connection with the usual achromatic structures, would appear to be quite as 
?CHATTON, Epovarp, Sur un mecanisme cinetique nouveau. La mitose syn- 
dienne chez les Peridiniens: parasites plasmodiaux. Compt. Rend, Acad. Sci. 173: 859- 
862. fig. I. 1921 
