VOL vox. 1 57 



veloped from a vegetative cell ; this enlarges, and being enclosed 

 by a single membrane, the spermatozoids perforate and enter it ; 

 thus fertilized the membrane increases in thickness, and the 

 spore becomes a resting spore which in due time germinates. 



Asexual propagation takes place by the division of larger 

 vegetative cells ( Parthenogonidia ) which produce new families; 

 these when sufficiently advanced separate from the mother cell 

 and enter upon independent life. 



Genus 32, VOLVOX, Ehrb. 



Coenobium spherical, continually gliding along with a rota- 

 ting motion ; looking like a hollow globe, the surface composed 

 of very numerous cells, gonidia, estimated as high as 12,000, ar- 

 ranged on the periphery at regular intervals, connected by a 

 matrical gelatin, having the appearance of a membrane in 

 which the gonidia are imbedded. Each gonidia is globose with 

 an outwardly-directed process bearing on the apex two long ex- 

 serted cilia extending beyond the common gelatinous envelope 

 by which the coenobium is circumscribed. By the waving of 

 the cilia the coenobium is kept in constant motion. The con 

 tents of the gouidia are chlorophyl-green including starch gran- 

 ules and often a red pigment spot. 



The oogonia are larger flask-like cells (gonidia) extending from 

 the periphery inwardly they are sustained by the neck-like 

 process bearing the cilia. The spermatozoids are produced in 

 cells similar in appearance and similarly located, as already de- 

 scribed ; the spermatozoids are spindle-shaped, furnished with 

 two cilia ; they fertilize the oogonium by penetrating the mem- 

 brane. The oogonia after a resting period, produce usually eight 

 zoogonidia ; the number is not regular, sometimes more or less. 



Asexual propagation takes place by the division of the larger 

 and darker flask-like cells, the larger end visible on the inner 

 surface of the walls of the coenobia ; the smaller neck-like end 

 extending outwardly bearing the cilia. These divisions aver- 

 aging about eight in number, soon round themselves and develop 

 the young Volvoxes in the mother cell. 



Within these young spheres, almost immediately after their 

 production, may be seen the selected gonidia for another genera- 

 tion, they being the larger gonidia, of darker green color than 

 the surrounding ones seen on the inside of the young coenobia. 



Viewing the vast multitude of the gonidia on the surface of 

 the sphere they appear to be detached, but upon a very close 

 observation under a high power and a carefully adjusted light, 



