56 COCCOPHYCE.E. 



Chlamydomonas pulvisculus. Ehr. Infus. p. 64. 



Macrogonidia ovate, twice as long as broad, or nearly ; deep 

 green, with a bright red lateral spot. 



SIZE. Diam."oo65--01o mm. 



Rabh. Alg. Sur. iii. 94. Colin in Nova Acta. xxiv. t. 18, f. 

 28. Fresenius Beitr. 235, t. 11, f. 43-45. 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 XXI. fig. 3. a, swartnspore ; &, c, encysted and undergoing 

 division ; d to g, gloeocystis forms ; /*, resting cells, after Cieukowski X 

 400 ; i, stellate cyst, from Stein ; j, individual differentiated ; k, swarm- 

 ing X 600. 



GENUS 39. VOLVOX. Linn. (1758.) 



Coenobium sphaerical, 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- 

 ccenobia 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 a summary of the structure and life-history, of 

 Volvox as given by A. W. Wills in the "Midland Naturalist" 

 (Sept.-Oct., 1880) : 



" It seems hardly necessary to describe the normal aspect of this 

 organism. Briefly, under a low power, it is seen to consist of a sphserical 

 globe of mathematical perfectness, so transparent that, as it glides 

 along, any object over which it passes is clearly visible through its 

 vacant spaces, i.e., through such parts as are not occupied by the struc- 

 tures presently to be noticed, while by focussing the binocular on the 



