32G SEXUAL GENERATION OF VAUCHERIA. 



to the extent of causing its endoclirome to be discharged. The 

 cilia are best seen when their movements have been retarded or 

 entirely arrested by means of opium, iodine, or other chemical 

 re-agents. The motion of the spore continues for about two hours ; 

 but after the lapse of that time it soon comes to an end, and the 

 spore begins to develope itself into a new plant. It has been 

 observed by Unger, that the escape of the Zoospores generally 

 takes place towards 8 a.m. ; to watch this phenomenon, therefore, 

 the plant should be gathered the day before, and its tufts examined 

 early in the morning. It is stated by Dr. Hassall, that he has 

 seen the same filament give off two or three zoospores successively : 

 their emission is obviously to be regarded as a method of increase 

 by gemmation, rather than as a generative act. 



246. Recent discoveries have shown that there exists in this 

 humble plant a true process of Sexual Generation, as was, indeed, 

 long ago suspected by Vaucher, though upon no sufficient grounds. 

 The branching filaments are often seen to bear at their sides 

 peculiar globular or oval capsular protuberances, sometimes 

 separated by the interposition of a stalk, which are filled with 

 dark endochrome ; and these have been observed to give exit to 

 large bodies covered with a firm envelope, from which, after a 

 time, new plants arise. In the immediate neighbourhood of these 

 ' capsules' are always found certain other projections, which, from 

 being usually pointed and somewhat curved, have been named 

 ' horns ' (Fig. 151, A, a) ; and these have been shown by Pringsheim 

 to be ' Antheridia, ' which, like those of the Characece (§ 255), 

 produce Antherozoids in their interior ; whilst the capsules (a, b) 

 are ' Germ-cells, ' whose aggregate mass of endochrome is destined 

 to become, when fertilized, the primordial cell of a new generation. 

 The antherozoids (b, c, d) when set free from the antheridium a, 

 swarm over the exterior of the capsule b, and have actually been 

 seen to penetrate its cavity through an aperture which opportunely 

 forms in its wall, and to come into contact with the surface of its 

 endochrome-mass, over which they diffuse themselves : there they 

 seem to undergo dissolution, their contents mingling themselves 

 with those of the germ-cell ; and the endochrome-mass, which had 

 previously no proper investment of its own, soon begins to form an 

 envelope (o, b), which increases in thickness and strength, until it 

 has acquired such a density as enables it to afford a firm pro- 

 tection to its contents. This body, possessing no power of spon- 

 taneous movement, is known as a ' resting-spore, ' in contradis- 

 tinction to the zoospores already described ; or it may be termed an 

 ' Oo-spore,' since it answers the purpose of a seed in laying the 

 foundation for a new generation, whilst the Zoospores merely 

 multiply the individual by a process analogous to budding. 



247. The Microscopist who wishes to study the development of 

 Zoospores, as well as several other phenomena of this low type of 

 vegetation, may advantageously have recourse to the little plant 



