REJUVENESCENCE IN NATURE. 209 



A total disappearance of the red colour not unfrequently 

 occurs. In the later stages of the cycle of generations 

 arrives, finally, the formation of microgonidia, already 

 mentioned (p. 138); many individuals, instead of pro- 

 ducing four daughter-cells, undergoing further division, 

 so as to give birth to a brood of sixteen or thirty-two minute 

 cells, which, before they separate, form a mulberry-like 

 body, but, separating at length, commence a very active 

 swarming inside the parent envelope, terminating in the 

 rupture of this coat, and the rapid dispersion of the 

 little "swarmers." These are of longer shape than the 

 large "swarmers," only about ^th, rarely 155th millim.long, 

 of yello,wish or dirty yellowish-green colour, with reddish 

 ciliated points.* They do not exhibit increase of size, 

 like the large " swarmers," never become coated with a 

 perceptible and loose membrane, and have no further 

 power of propagation. Most of them die after they have 

 settled to rest, dissolving away; others turn into little 

 red globules, and it is doubtful whether they can grow up 

 to the normal size. If we now further examine how the 

 cycle of active generations is closed and carried over to 

 the resting vegetation, we find that the large " swarmers" 

 of the last active generation, when their growth is 

 completed and they have attained the stage of rest, 

 instead of dividing again, remain undivided, assume a 

 perfectly globular form, and in the course of a few days 

 become clothed by a thick, closely applied cell-membrane, 

 while the earlier, loose, distant membrane gradually 

 disappears. The contents, which at the commencement 



counting the Volvocinese (Volvox, Paiidorina, Botryocystis Morn in ?.) In 

 the genus CUamidomonas there are species with and others without the red 

 point. The red point seems to be absent in Vauclieria, (Edogonium, Bid- 

 bockcBte, Conferva bomhycina, Aphanochate, Qongrosira, Ascidiitm, Characinm., 

 Sciadmm, Pediastrum, Apiocystis, Diciyosphoerium, Tetraspora, Pjotocoocws 

 viridis, Qlceococcus. The minute size and light colour may have caused it to 

 have been overlooked in many cases. 



* Heematococcus plavialis porphyrocepalus, Von Plotow, 1. c., p. 469, 

 t. XXV, f. 74. I must observe, however, that I have never observed the 

 hammering movement of the slender red anterior end, there described ; the 

 motion was effected, as in the large swarmers, by two cilia, which became 

 visible by the application of tincture of iodine. 



14 



