VOLVOCINE^E. 51 



Chlamydococcus pluvialis. Br. Rejuvenescence, p. 206. 



Cells subglobose, very variable in size, brownish red, chang- 

 ing in some conditions to green. 



SIZE. Cells -007--035 mm. 



Babh. Alg. Eur. .iii, 93. Cohn Nova Acta. xxii. p. 749, 

 t. 67 A. B. Pritchard Infus. 523, t. xix. f. 20-31. T. C. 

 White, in " Qnekett Microscopical Journ.," vi. p. 43. 



Hcematococcus pluvialis. Flotow, Nova Acta xx. 



Hcematococcus Corda. Meneg. Nost. p. 20, t. 1, f. 5. 



Hcematococcus mucosus. Morren Rubefact : des Eaux, t. 6, 

 f. 10-20. 



Frotococcus pluvialis. Kutz. Tab. i. f. 1. Cohn, Memoir 

 on Protococcus. 



Protococcus monospermus. Corda, in Sturm Flora ii. 25. 



On rocks, stones, &c., in hollows filled with rain water. 



" Normally fully developed cells of this multiform creature, sometimes 

 like a plant, sometimes like an animal, present the ^appearance of glo- 

 bules from -02 to '04 mm. diam., with a thick, tough cell membrane, and 

 granular-punctate, opaque contents, sometimes of a brown, sometimes (at 

 other periods, or in other localities) bright red colour. In the mass of 

 the dark contents lie hidden several other structures, which at this period 

 are completely concealed, namely 4-6 starch globules of '0033 or at 

 most '005 mm. in diameter, in which, as in those of Hydrodictyon, a 

 nucleus and an envelope may be distinguished, acquiring a violet colour 

 with iodine, the nucleus becoming rather redder. Sulphuric acid causes 

 a considerable swelling up of the coat. There also appears to exist in 

 the centre of the cell a large, very delicate nuclear vesicle, which, how- 

 ever, is so covered up by the rest of the cell contents, that it can only 

 be very indistinctly perceived, and cannot even be clearly displayed 

 when the contents are squeezed out. When these resting globular cells 

 are placed in water they give birth to four gonidium-like swarming 

 cells. Even before the commencement of the division of the contents 

 by which the latter are formed, a change begins in the colour of the 

 parent cell, the red colour retreating to some extent from the periphery, 

 and a yellow (sometimes rather greenish) border forming round the deep 

 red inner mass. The young swarmers also, for a short time after they 

 issue out, have only a narrow yellow rim round a dark red middle. 

 During the two or three days' period of movement and growth of these 

 swarming cells in which they grow to about four times the original 

 size, changing their obtusely ovate form at the same time to a reversed 

 pear-shaped apiculated shape important new changes take place in the 

 contents of the cells. The red colour becomes more and more concen- 

 trated into the middle of the cell, so that a sharply defined bright red 

 nucleus is formed, in the interior of which a lighter space is often 

 clearly perceptible, corresponding to the nuclear vesicle above-men- 

 tioned, around which the red colouring matter forms a covering, mostly 

 complete, but sometimes imperfect and interrupted. The rest of the 

 cell contents have become a brilliant green, and in them may be clearly 

 distinguished the above-mentioned starch granules, as well as many 

 more smaller green granules. The ciliated point of the cell, often 

 drawn out like a beak, is colourless. This first moving generation is 

 succeeded by a not yet accurately determined number of similar active 

 generations populating the water for some weeks, and often giving it a 

 bright green colour, till at length universal rest recommences, and the 



