464 FREDERICK KEEBLE. 
brown alga, nothing of certain value can be said as to the 
systemic position of this organism. It is evidently distinct 
from the Zooxanthelle of Radiolarians. For, whereas these 
yellow-brown cells possess two chloroplasts, the infecting alga — 
of C. paradoxa possesses, in its fully-developed state, a 
large number (ten or more); and, whereas the reserves of 
Zooxanthelle consist of starch or some undetermined sub- 
stance, those of the infecting alga of C. paradoxa consist 
of fatty globules. 
The pigments of the algal cells consist of a yellow-brown 
substance soluble in water and probably similar to Phyco- 
chrysin, a pigment described by Gaidukov as occurring 
together with a chlorophyll-like, green pigment in Chromu- 
lina rosanoffii a member of the Chrysomonadinex. 
The brilliant emerald-green reaction given by the yellow- 
brown cells when treated with strong sulphuric acid is stated by 
Zimmermann to be given also by Diatomin, the brown pig- 
ment of the Diatomaceee. The fact that the pigments of the 
Chrysomonadinee are held to be allied to those of the diatoms 
gives some slight indication that perhaps the yellow-brown 
alga of C. paradoxa may prove to be allied to the Chryso- 
monadinee rather than to the Cryptomonadinez, to which 
group the Zooxanthelle of Radiolaria have been referred ; 
but the evidence is too slender to admit of more than a con- 
jecture. 
(g) The Significance of the Relation between 
Animal and Yellow-brown Cell.—The facts set forth in 
the preceding pages have demonstrated the intimacy of the 
relation between C. paradoxa and its yellow-brown cells. 
So dependent is the animal on these cells that, apart from 
them, it is incapable of growth or development. Larve 
which escape infection, although they take up solid food, fail 
to develop, decrease steadily in size and die. In like manner 
the algal cell, once in the body of C. paradoxa, becomes an 
integral part of that body, and is no more capable of inde- 
pendent existence than is any somatic cell of the animal. The 
yellow-brown cell stands to the animal cells in the same rela- 
