214 MURIEL ROBERTSON. 
gether satisfactory, partly owing to the Volvox not thriving 
in the small volume of water, partly on account of the inroads 
of bacteria. I finally found that Pseudospora could be got to 
live quite normally for a week to a fortnight on slides with a 
circular moat hollowed out round the part where the object 
to be observed was laid. Spirogyra was placed in the moat, 
and the whole covered with a supported coverslip. The edges 
of the coverslip were then sealed up with vaseline. 
The preserved preparations, with very few exceptions, 
were stained under the coverslip and mounted in balsam. 
The stains used were: Ehrlich’s hematexylin, iron hema- 
toxylin (Heidenhain’s), borax carmin, picrocarmin, safranin, 
and Romanowski’ stain. Paracarmin was tried, but never 
gave good results. Orange G., methylene blue, and eosin 
were also not, as a rule, very successful. 
Mitosis was followed out on corrosive material stained 
with Ehrlich’s hematoxylin and checked by osmic material 
stained with Ehrlich’s hematoxylin and picrocarmin. For 
the observations on the development of spheres, Romanowski, 
safranin, and Ehrlich’s hematoxylin were used, the best 
results being obtained with Romanowski, which proved, how- 
ever, to be an exceedingly difficult stain to use. 
Pseudospora volvocis was first named by Cienkowski in 
1865 (‘ Archiv f. mikr. Anat.’, vol. i, p. 214) ; he described a 
flagellate and an amceboid form, and also a definite double- 
walled cyst, surrounded by a gelatinous veil. As will appear 
later, I have been unable to find this encysted form. Biitschli 
in Bronn’s ‘Klassen und Ordnungen,’ 1883, places Pseudo- 
spora amongst the Isomastigoda, but does not describe its 
life history. 
Zopf, in his work on ‘Die Schleimpilze,’ mentions it 
under the name of Diplophysalis volvocis, and refers to 
Cienkowski’s paper. The next reference is in Klebs’ ‘Flagel- 
laten Studien,’ 1892, where he points out the ambiguous sys- 
tematic position of the genus. The group to which Pseudo- 
spora belongs seems from the literature somewhat neglected 
since Zopf’s work on ‘ Die Schleimpilze.’ 
