324 PEOFESSOB W. C. WILLIAMSON ON VOLVOX GLOBATOE. 



mass of lining membrane and endochrome, which diminishes 

 as the radiating processes become elongated. 



Owing to these changes, the green cell-contents assume 

 a stellate form {Fig. 4 a), and the intermediate transpa- 

 rent spaces become proportionately enlarged. This ex- 

 pansion of the cell- wall, and elongation of the thread-like 

 processes of the lining membrane, go on until we have the 

 appearance presented by Fig, 5, in which state the central 

 green cell {Fig. 5 a) is seen to be much reduced in size, 

 as well as altered in shape — having become more triangu- 

 lar ; whilst the processes {Fig. 5 b) attaching it to its outer 

 cell-walls, are elongated, and often branched. In this stage 

 it is very rarely possible to trace the outlines of the original 

 hexagonal cells. I have, however, been able to identify 

 them sufficiently often to establish their existence. By 

 rupturing a Volvox under water containing a slight trace of 

 tincture of iodine, and at the same time paying great at- 

 tention to the management of the light, I have seen them 

 with great distinctness, as represented by the faint lines, 

 Fig. 5 c ; each one containing its own endochrome. The 

 projecting threads which maintain the inner cell in its posi- 

 tion {Fig. 5 h), and which are usually attached to the 

 cell-walls at points exactly opposite the corresponding 

 processes of adjoining cells, give the whole the appearance 

 of continuous canals, connecting together the separate 

 masses of endochrome. It is in this light that they were 

 r^arded by Ehrenberg, who appears never to have seen 

 the hexagonal cells within which they are enclosed, and 

 the thin cell-walls of which intervene between the opposite 

 extremities of apparently continuous threads. 



During the progress of these transitions from the angular 

 to the stellate form, corresponding changes are affecting the 

 character of the other cell-contents. In the early stages of 

 growth, each cell, as already stated, contains an abundance 

 of dark green endochrome, along with numerous minute 



