228 MURIEL ROBERTSON. 
T have made no attempt to reconcile the formation of 
spheres as I observed it in Pseudospora with the sporocysts 
described by Zopf in Polysporella, Pseudospora aculeata, 
Vampyrella, and other forms. The true test of their similarity 
would lie in the relations of the nucleus in spore formation. 
As to the behaviour of the karyosome in sphere formation 
Hertwig (‘ Archiv f. Prot.,’ vol. i, 1901) refers to a some- 
what analogous form of nuclear multiplication where “ in einem 
grossen, oft so gar riesigen Mutterkern zahlreiche Tochter- 
kernanlage entwickelt werden, welche in dass umgebende 
Protoplasma heraustreten wihrend der Mutterkern zu grunde 
geht.” In sphere formation we have an essentially similar 
process, only here the cell bodies for the daughter nuclei are 
not derived directly from the maternal cytoplasm but from 
protoplasm built up within the original nuclear membrane. 
Part of the achromatic portion of the maternal nucleus appears 
indeed to become converted directly into a mass of rapidly 
growing protoplasm. 
In Pseudospora the nucleus is more specialised than in the 
form described by Hertwig, and a definite part, the karyosome, 
is ejected when the nuclei of the spheres are formed. 
The phenomena of sphere formation in Pseudospora serve 
to accentuate the close relationship between the achromatic 
part of the nucleus and the protoplasm of the surrounding 
cell-body. 
The tendency of recent work on the Protozoa appears to be 
to accentuate the importance of Doflein’s main subdivision 
Plasmadroma, and, on the other hand, to point towards the 
possibly artificial character of the subdivisions of the Plasma- 
droma. Pseudospora with its amceboid, heliozooid, and flagel- 
late phases accentuates this. It seems clear that taxonomic 
distinctions resting on observations of anatomical features 
during one phase of the life history are so unreliable as to be 
almost worthless. Such characters are shown by the transfor- 
mation of “species” of Amceba into one another by slight modi- 
fication of the external conditions to be of the most superficial 
kind, being mere morphological reflections of surrounding 
