PROFESSOR W. C. WILLIAMSON ON VOLVOX GLOBATOE. 325 



granules of an uncertain nature, but apparently analogous 

 to those seen in so many of the fresh-water Algaj. After a 

 while, a single large green granule {Fig. 3 and 4 V) makes its 

 appearance in each cell, whilst many of the minute ones, 

 previously observed, disappear. One or two of the latter, 

 however, not only remain unabsorbed, but continue to 

 enlarge; and from their pale colour, and high refracting 

 power, become very brilliant (Fig. 5 a and 12 a). The large 

 green granule now disappears in its turn, whilst a new feature 

 becomes increasingly conspicuous : this is the celebrated red 

 spot which Ehrenberg regards as the eye of his animalcule. 

 For some time I thought that the latter object was the 

 direct result of a transmutation of the former granule, so fre- 

 quently did the appearance of the one mark the disappear- 

 ance of the other; but this is not the case. They are perfectly 

 distinct, though the red speck is rarely to be seen when the 

 green granule is fully developed, or even beginning to be 

 absorbed. On the disappearance of the latter object, we find 

 that the remaining green endochrome has assumed a paler 

 hue; but the one or two brilliant granules {Fig. 5 f, 12 a) 

 just referred to, have materially increased in size and con- 

 spicuity, occupying a large proportion of each green central 

 area. In fact the only contents of the latter, in the present 

 stage, are the granules, the red spot, and a small quantity 

 of pale green homogeneous endochrome. 



The brilliant points, which are the generative organs of 

 Ehrenberg, are perfect and well-defined spheres; but I 

 have not been able, by any adjustment of the instrument, 

 to obtain so definite an outline to the eye spot {Fig. 5 d and 

 12 6) of the Prussian naturalist. It appears to be the result 

 of an alteration in the condition both of the lining mem- 

 brane, and of some of the granular cell-contents which ad- 

 here to it. The degree of its distinctness is very variable. 

 In some specimens its presence is barely to be detected, 

 even in the most advanced condition of the cells. 



