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PSEUDOSPORA VOLVOCIS, CIENKOWSKI, 21 
Pseudospora volvocis, Cienkowski. 
By 
Muriel Robertson, 
Zoological Laboratory, University of Glasgow, 
With Plate 12. 
I wave adopted the name “ Pseudospora volvocis ” for the 
protozoon here discussed, as the two most obvious phases 
correspond with the creature described under that name by 
Cienkowski. 
Pseudospora was noticed amongst Volvox, supplied by 
Mr. T. Bolton to the Cambridge laboratory and, later on, to 
Glasgow. As the creature showed features of considerable 
interest and the knowledge of its life history appeared to be 
very imperfect, it seemed advisable to make it the subject of 
special investigation. 
I wish here to acknowledge my great indebtedness to 
Professor Graham Kerr. This paper, which was begun at 
his instigation, would certainly never have been completed 
but for his kind supervision and guidance. 
All the processes described were followed out on the living 
specimens and checked by stained preparations. The investi- 
gations were made for the most part on material mounted on 
slides under cover-slips supported with wax. It was impos- 
sible, however, to keep slides of this description under obser- 
vation for more than twelve to eighteen hours, as after that 
period the Pseudospora invariably died. Cultures in watch 
glasses, even when kept in a damp chamber, were not alto- 
