CHLOROPHYCEA 185 
blance to the encysted condition of some Pert- 
diniee on the one hand, and on the other is not 
without a suggestion of likeness to the Desmids, an 
order of beautiful unicellular Algee known only in 
fresh-waters. The forms are globular, 0°6 to 08 
mm. in diameter, and spindle-shaped, with a 
colourless membrane, showing some resemblance 
to that of Ceratiwm. The nucleus is eccentric, 
and connected by fine strands of protoplasm with 
the protoplasm that lines the membrane. The 
chromatophores are small yellow plates. Pyrocystis 
thus differs entirely from the Desmids in the 
colouring matter and disposition of the protoplasmic 
contents. The indication of division in Fig. 57, ¢, d, 
is the only known mode of reproduction. 
CoccOSPHERES AND RHABDOSPHERES. 
These names have been given to exceedingly 
puzzling organisms which occur in vast abundance in 
the ocean. There appears to be little room for doubt 
that they are calcareous unicellular Alge. They 
occur in all surface and subsurface waters of 
tropical and temperate seas beyond the in- 
fluence of coast waters, and are often found 
entangled in the protoplasmic matter of Foram- 
intfera and Radiolaria, in-the stomachs of Crus- 
tacea and Salpe, as well as free in large numbers 
in the water. The Rhabdospheres are tropical and 
the Coccospheres temperate, though the latter occur 
within the tropics as well, but not so abundantly. 
