T. C. WHITE OX PUOTOCOCCTTS PLUVIALI3. 45 



it rolls over slowly, and although it is not clear what occupies its 

 centre when the red is absent or diffused, yet its walls contain many 

 vacuoles or vesicles, together with granules of varying size. With 

 these motile forms of Protococcus, you will observe some that are 

 three or four times larger, perfectly circular, and filled entirely by a 

 ruby-coloured, highly refractive protoplasm. The bridge by which 

 the motile forms pass over to this resting stage seems at present 

 unrecorded, and although I have watched them very narrowly, I 

 have failed in seeing any transitional stage in their developmental 

 history, but I have noticed in the summer time that these resting 

 spores have become granular and less refractive, and the ruby tint 

 has become paler in a band crossing the cell diametrically, and this 

 has again, a little later, been crossed almost at right angles by 

 another light band, as if the red colour was becoming thinner in 

 these lines — the green colour meanwhile becoming for the first time 

 visible in the light bands ; after a few hours the bands have become 

 separations, while the red matter became defined as a central mass 

 in each quarter of the sphere, and was surrounded with a coating of 

 green. Now the sphere becomes more or less ovoid, and a bulging 

 of the wall occurs at the small extremity of the egg-shaped cell ; 

 meanwhile rotatory movements are seen within, the future macro- 

 gonidia preparing themselves for their independent existence. 

 Suddenly the thinned side of the cell bursts, and the four 

 imprisoned gonidia swim away by means of what seems a fringe of 

 cilia. Professor Cohn doubted the existence of this process of self- 

 division, but Mr. F. Currey, in an article contributed in 1858 to the 

 '^Microscopical Journal" avers that he had seen it. He says, he 

 *' has distinctly observed it," and I can fully corroborate his observa- 

 tions. Some resting spores of this Alga divide into many smaller 

 gonidia, and I believe from what I have seen that these constitute 

 the so-called Frotococcus nivalis, or red snow, as I have had an 

 abundance of this plant develop, where before I only had the motile 

 forms of P. pluvialis ; but though these spores are small at first, 

 they seem to grow by the imbibition of nourishment from the water, 

 and become the same size as the red resting spores to which I first 

 alluded. 



The specimens under my microscope present several stages ; you 

 will see the moving Protococcus varying in size from j-^-qq to ^oVo- 

 of an inch, and by careful adjustment of the light may detect its 

 structureless cyst and the two flagella ; you will also see its 



