CIILOROPHYCE^E 185 



blance to the encysted condition of some Peri- 

 dinicce on the one hand, and on the other is not 

 without a suggestion of likeness to the Desmids, an 

 order of beautiful unicellular Algae known only in 

 fresh-waters. The forms are globular, 0'6 to 0'8 

 mm. in diameter, and spindle-shaped, with a 

 colourless membrane, showing some resemblance 

 to that of Ceratium. 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, c, 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 Algae. 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 Fwam- 

 inifera and Radiolaria, in the stomachs of Crus- 

 tacea, and Salpce, 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. 



