Palmellacece 243 



Sub-family II. TETRASPORE.E. 



The cells are usually grouped in fours, or more rarely irregu- 

 larly disposed, towards the periphery of a structureless mass of 

 jelly. The sub-family is distinguished from the Palmellese and 

 the Gloeocystidese by the ' pseudocilia ' which are attached in 

 pairs to each cell. 



Genus Tetraspora Link, 1809. [Indus. Stapfia Chodat, 1897.] 

 The colonies are gelatinous, macroscopic or microscopic, indefinitely 

 expanded or more or less intestiniform and convoluted. The cells 

 are spherical, distributed without order near the periphery of the 

 enveloping jelly or grouped in twos and fours. In structure the 



S- S c 



of. A* 



o" 9 < 



' CP S> &> D 



~-<5> B 



Fig. 111. Tetraspora lubrica (Roth) Ag., from near St Just, Cornwall. A, nat. 

 size; B, portion of colony, x 100 ; C, x450; D, zoogonidium, x 450. 



cells are similar to those of Palmella, with the addition of two 

 (or more rarely four) ' pseudocilia.' Multiplication takes place 

 by repeated division of the cells, chiefly in two directions in one 

 plane, with the gelatinization of the mother-cell-walls. Reproduc- 

 tion occurs by biciliated zoogonidia and isogamous planogarnetes. 

 Hypnospores, 'with thick cell- walls of a brown colour, are also 

 produced. 



Several 'species' of this genus occur in the stagnant waters of the British 

 Islands, but it is very doubtful if they are specifically distinct. T. gelatinosa 

 (Vauch.) Desv. is the commonest form, with a vesicular gelatinous colony and 

 cells 6 12 /i in diameter. T. lubrica Ag. (fig. Ill) and T. explanata Ag. are 

 most probably other forms of this species. T. lacustris Lemm., which is a 

 form confined to the plankton, is possibly a stage in the life-history of Sphcero- 

 cystis Schroeteri Chod. 



162 



