56 COCCOPHYCES. 
Chlamydomonas pulvisculus. LZhr, Infus. p. 64. 
Macrogonidia ovate, twice as long as broad, or nearly ; deep 
green, with a bright red lateral spot. 
Size. Diam. :0068-:013 mm. 
Rabh. Alg. Eur. iii. 94. Cohn in Nova Acta, xxiv. t. 18, f. 
28, Fresenius Beitr. 235, t. 11, f. 48-45. Pritchard Infus. 
521, t. 18, f. 40, 51-54. 
Diselmis viridis, Dujard. Zoophy. 342 iii. f. 20, 21. 
In stagnant water. 
“These creatures form a large portion of the green matter which 
colours the water contained in water-butts, ponds, and puddles in the 
summer and autumn, especially after a storm. Whenever these exist in 
large quantities, multitudes of them, and of their envelopes, rise to the 
surface of the water, and form a green stratum upon it.”— Pritchard, 
Plate XXT. fig. 3. a, swarmspore; 6, e, encysted and undergoing 
division; d to g, gloeocystis forms; h, resting cells, after Cienkowski X 
400; i, stellate cyst, from Stein ; j, individual differentiated ; #, swarm- 
ing X 600. 
Genus 89. VOLVOX. Linn. (1758.) 
Ceenobium spherical, continually rotating and moving, look- 
ing like a hollow globe, composed of very numerous cells 
arranged on the periphery at regular distances, connected by 
the matrical gelatin ; furnished with a red lateral spot, two 
contractile vacuoles, and two long exserted cilia, all circum- 
scribed within a common hyaline vesicle. Propagation sexual 
or non-sexual. In the non-sexual certain distant cells greatly 
enlarge, divide into numerous parts, and evolve daughter- 
ceenobia within the parent-ccenobia, which are ultimately set 
free. In sexual propagation certain masculine cells undergo a 
multipartite division into fascicles of mobile spermatozoids | 
which are contractile, pear-shaped, and biciliate, afterwards 
free. The female cells are enlarged, but do not undergo 
division ; after fertilization they develop into motionless 
oospores, which are finally red, surrounded by a double epi- 
spore. 
The following is 4 summary of the structure and life-history, of 
Volvo» as given by A. W. Wills in the “Midland Naturalist” 
(Sept.-Oct., 1880) :— 
“Tt seems hardly necessary to describe the normal aspect of this 
organism. Briefly, under a low power, it is seen to consist of a spherical 
globe of mathematical perfectness, so transparent that, as it glides 
along, any object over which it passes is clearly visible through its 
vacant spaces, ¢.e., through such parts as are not occupied by the struc- 
tures presently to be noticed, while by focussing the binocular on the 
