1 90 VOL VOX GL OS A TOR. PART n. 



In the interior of the sphere there are from two to 

 twenty dark green globes of different sizes ; the smaller 

 are attached to the internal surface, while the larger 

 rotate freely by their cilia in the internal cavity. After 

 a time the sphere bursts open and its inhabitants swim 

 forth, and soon assume the form and character of that 

 which gave them birth. 



The growth and development of the Volvox globa- 

 tor are peculiar, for in the primordial cell the red and 

 green endochrome breaks up into numerous angular 

 masses, and a central globe rather larger than the rest. 

 The angular masses are connected by green threads, 

 the interstices between all the bodies are filled with a 

 hyaline substance secreted from their surfaces, and the 

 whole is enclosed in a distinctly membranous globular 

 envelope. 



As this young Volvox increases gradually in size, the 

 hyaline matter is increased, the green threads lengthen, 

 and the angular masses assume the form of a flask the 

 __j__th of an inch in diameter exactly as in the Protococ- 

 cus ; for the green matter with a few red spots is collected 

 in the thick end, while the hyaline beak is turned towards 

 the circumference of the sphere, which is pierced by their 

 long cilia. Each of them is invested with a pellucid 

 envelope of considerable thickness, the borders of which 

 are flattened against those of similar envelopes. While 

 these ciliated bodies are approaching maturity their en- 

 dochrome exhibits vacuoles or apparently empty cavities 

 of a spherical form about one-third of its own diameter. 

 Mr. G. Busk discovered that these vacuoles expand and 

 contract at regular intervals of about forty seconds. 

 The contraction, which almost obliterates the cavity of 

 the vacuole, is rapid and sudden ; the dilatation is slow 

 and gradual. This action ceases when the body comes 

 to maturity. 



When this mass of zoospores connected by green 



