28 



DIPS INTO MY AQUARIUM. 



an object well worthy of being sought after, and, fortunately, it 

 can be obtained at almost any time in the year. It is, however, 

 somewhat fickle in its attachments, for in localities where it has 

 been found repeatedly, it will at another time be sought in vain, 

 although there is apparently no reason for its disappearance. 



Now, look at it through this half-inch objective. Did you ever 

 see anything more lovely ? Watch that gracefully-rolling sphere 

 as it slowly revolves on its axis across the field of view ; notice its 

 delicate tracery, forming the boundary-lines of six-sided cells ; 

 observe the profusion of pear-shaped dots, from whose apices are 

 projected those very fine gossamer-like hairs, or cilia, which pene- 

 trate right through the outer envelope and with swift movement 

 row the Volvox along, and tell me whether even Nature's casket 

 contains any gems more wondrously fair. Within the globe are 

 smaller globes. With a higher magnification these are seen to be 

 growing Volvoces, and not infrequently there may be found within 

 these a third generation, all carrying on their marvellous gyrations 

 within the parent-cell. After awhile, the mother, or the grand- 

 mother, will grow weary with age and cease her activities. She 

 will lose her fresh greenness and perish ; and the young, panting 

 for liberty, will break through her ruptured sides and escape into 

 the tiny water-world where they were born. 



Under still higher powers, and with the help of a weak 

 staining agent — such as iodine and diluted sulphuric acid — it will 

 be seen that the green spots are united by extremely fine proto- 

 plasmic threads, which pass through the sides of the hexagonal 

 cells. There may also be detected minute atoms of colourless 

 protoplasm, which is probably the agent of cell-division. When 

 the cell is ripe, it opens without abruptness as if there were a 

 natural vent which is gradually prepared for this crisis, and the 

 ensphered young glide out. At first, they are tied to the parent 

 by long filaments, which prevent revolution ; but soon the threads 

 give way, and the sweets of perfect liberty are tasted. Whether 

 there is actual revolution of the young within the parent globe, or 

 whether the apparent revolution is due to an optical illusion caused 

 by the motion of the mother-cell, is a point on which authorities 

 differ, and is one about which I am not prepared to pronounce 

 dogmatically. 



