336 PROFESSOR W. C. WnxIAMSON ON VOLVOX GLOBATOR. 



tained four of these large granules, and which assumed the 

 characteristic purple colour under the influence of iodine. 

 In this example they were surrounded by minute dark- 

 coloured granules in an active state of molecular motion, 

 though themselves perfectly quiescent. In many Desmi- 

 diaceae, however, I have failed to effect any change in the 

 colour of the granule by the addition of iodine, beyond that 

 produced upon the Volvox when similarly acted upon, viz., 

 the conversion of the pale green hue into a varying tint of 

 brown. From these circumstances, I have little doubt that 

 the granule possesses the same nature and functions in all 

 these known vegetable forms, and in the Volvoa;. It does 

 not ultimately become converted into a mass of starch in 

 many true plants, though it is in a number of instances ; 

 consequently, the absence of the violet hue in the cells of 

 Volvoja, when they are acted upon by iodine, neither militates 

 against their vegetable nature, nor against my conclusion, 

 that the large green granule is identical with that seen in 

 the cells of a young Zygonema. What may be its use I 

 know not ; but in all these cases it assumes the same form 

 as in the Volvoa; ; not existing in the first instance, but 

 being gradually developed ; and after fulfilling its office, 

 whatever that may be, it is re-absorbed before the plant 

 arrives at maturity. 



The red speck to which Ehrenberg has assigned the 

 functions of an organ of vision, is also known to exist 

 in the ciliated moving zoospores of Conferva glomerata and 

 C. ciliaris. Of the vegetable character of these spores there 

 can be no doubt ; consequently we must not only reject 

 the physiological conclusion of the Prussian professor, but 

 cease to regard the red speck as an indication of animal life. 



The peculiar appearances presented by the shrinking of 

 the endochrorae and inner cell-membrane, as seen in Mg. 11, 

 are identical with those exhibited by Pediastrum, Cocco- 

 chlorisy and numerous other Confervae, when subjected to the 



