Objects for the Microscope. 51 



of water ; revolving round and round, sometimes gliding 

 along, sometimes rolling through the water, a transparent 

 globe, enclosing from one to seven, or even twenty, lesser 

 and darker green globules, of various sizes. Each of those 

 globules in time breaks from its parent cell, and becomes 

 likewise a mother plant, producing young volvoces with 

 such rapidity that ponds are often thronged with them, 

 and the water is coloured to a deep green. There is a 

 pond at Blackheath which, in the months of July and 

 August, abounds with Volvox globator. 



CLOSTERIUM 



is a favourite specimen of Desmidiacese. Its little half- 

 moons, or ovals, sometimes joined together, are frequently 

 found in all pools, especially on moors and in exposed places. 



Lately the Closterium has been closely examined with 

 high powers, and a circulation of fluid was seen throughout 

 the cell. This requires a power of 300 diameters and care- 

 ful management of light. Then a peculiar whirling move- 

 ment may be distinguished in the large round space at the 

 end of the cell, as well as along both the concave and con- 

 vex edges of the Closterium. It is like the circulation in 

 Vallisneria, Chara, and Anacharis, which I do not describe, 

 because I am only noticing those objects which are mounted 

 for students, in the hope of leading them to examine the 

 living plants for themselves, with other books of a higher 

 order. (Read ' Carpenter's Microscope/ chap, vi., on the 

 Desmidiacea?.) 



To find the Desmidiacea?, try small shallow pools, and 

 not stagnant water. 



The Closterium, Euastrum, Micrasterias, &c., will be 

 found as a gelatinous stratum at the bottom, on stones, or 

 stems of water-plants. The Staurastrum, Pediastrum, and 

 all the smaller species, float as a thin film on the water, or 

 form a dirty-looking cloud round the aquatic plants. 



Raise the film with a small muslin net, or pour the water 

 through your handkerchief, scrape off the deposit, and trans- 

 fer it into bottles of fresh water for examination at home. 



