DIVISION OF COLLAR-CELLS OF CALCAREA HETEROCCELA. 137 
broad fundamental theory rather than as a complete explana- 
tion of all the facts. They have, however, the great merit of 
being formulated from physiological as well as morphological 
observations, and therefore pay due regard to the processes 
of cell-life. Yery probably the cytoplasmic substance must be 
regarded as much more complex than is suggested in Hertwig’s 
survey. It is interesting to note in this connection that the 
work of Reichenow (4) has shown that the substance called 
volutin, which arises in the cytoplasm, is a stage in the 
building up of the nuclear chromation — or to put the matter 
more precisely, the chromatin in the nucleus increases at 
the expense of the volutin in the cytoplasm. The point in 
this description of Hertwig's view that I wish to emphasise is 
that it brings out very clearly the achromatic nature of the 
centrosome. In a later part of the same article he goes on to 
say that “ die Centrosomen und die Basalkorperchen von 
Wimpern, Geisseln und Pseudopodien analoge Gebilde sind.” 
The proposition embodied in the last sentence has received 
additional proof and has been further extended by practically 
all the recent work upon the subject. 
Lister Institute, 
May, 1911. 
Literature. 
1. Hartman and Chagas. — “ F lagellaten - stu d ien , " * Memorias do 
Instituto Oswaldo Cruz.,’ Tomo 2, Facie. 1, April, 1901. 
2a. Hartmann and Prowazek.— “ Blepharoplast, Caryosom, und 
Centrosom.'’ * Arch. f. Protistenkunde,’ Bd. x, 1907. 
3. Hertwig. — “ Die Protozoen und die Zelltheorie.” * Arch. f. Protis- 
tenkunde. Bd. i, 1910. 
4. Reichenow. — “ Hsemogregarina stepanowi,” ‘ Arch. f. Protis- 
tenkunde, Bd. xx. Heft 3, 1901. 
5. Robertson and Minchin. — “ The Division of the Collar-cells of 
Clathrina coriacea,” .* Quart. Journ. Micr. Sci.,’ vol. 55, part 
4, November, 1910. 
