242 



CMorophycece 



occurs in very extensive gelatinous masses, often several cms. in diameter, 

 whereas the colonies of S. delicatula are very much smaller, rarely exceeding 

 a diameter of 300 /^. The latter species has also a distinct preference for 

 Sphagnum-pools. 



Genus Sphaerocystis Chodat, 1897 l . The cells are globose 

 and sparsely aggregated within a free-floating globular mass of 

 very transparent jelly. The number of cells within each gelatinous 

 sphere varies from 1 to 16 (or more), and they are usually disposed 

 towards the periphery. Sometimes there is a slight indication of 

 lamellation in the jelly immediately surrounding the cells. The 



. - 



C 



Fig. 110. Sphccrocystis Schroeteri Chod. ; A and B, from the plankton of Loch 

 Shin, Sutherland, x450; C, zoogonidium, after Chodat ( x about 700). 



methods of multiplication are : 1st, by division of the cells into 

 four daughter-cells, either in one plane or tetrahedrally disposed ; 

 2nd, by the rupture of the walls of a sporangium containing a 

 number of daughter-cells, with a slight retention of the old walls 

 of the mother-cells as in Schizochlamys ; 3rd, by the formation of 

 biciliated macro- and microzoogonidia. This genus very closely 

 resembles Gloeocystis Nag. 



Sph. Schroeteri Chod. is an abundant Alga in the freshwater plankton, 

 occurring in all the larger lakes of the British Islands ; diam. of colonies 50 

 1200 /LI; diam. of cells 6 10 p.; fig. 110. Chodat regards both Tetraspora 

 lacustris Lemm. and Botryococcus sudeticus Lernm. as stages of this plant. 

 With regard to the former he is possibly correct, but the latter is a close rela- 

 tive of Botryococcus Braunii and certainly has no affinity with Xphcerocystis. 



1 Chodat in Bull. Herb. Boissier, 1897, p. 292, t. ix. 



