VAUCHERIA. 



[ 671 ] 



VAUCHERIA. 



motion around its own axis, and it exhibits 

 a remarkable elasticity of structure, giving 



Fig. 798. 



Fig. 799. 



Vaucheria Ungeri. 



Fig. 798. End of a filament in which a gonidium is 

 being developed. 

 Fig. 799- Gonidium escaping from the filament. 



Magnified 50 diameters. 



way and altering its form (fig. 799) to squeeze 

 tlirougli the narrow orifice of escape ; some- 

 times it becomes "pinched" in this process 

 into two independent gonidia of half the 

 usual size. As soon as it has perfectly 

 emerged, it assumes an elliptical form, in- 

 creases much in size, and is seen to be co- 

 vered with innumerable vibratile cilia (fig. 

 801), arising from its gelatinous (protoplas- 

 mic) coat (these are rendered much more di- 

 stinct by applying tincture of iodine) ; no 

 cellulose membrane exists at this time, and 

 the gonidhim swims about actively in the 

 water, revolving on its long axis. The large 

 number of ciUa existing on this gonidium 



Fig. 800. 



Vaucheria Ungeri. 



Fig. 800. End of the filament from which the gonidium 

 has escaped. Magnified 50 diameters. 



Fig. 801. Gonidium which has been treated with iodine 

 and dried between two slips of glass, showing the cilia 

 very clearlj'. Blagnified 110 diameters. 



distinguish it remarkably from all others; 

 but we are inclined to believe that there is a 



nearer relationship than appears at first sight. 

 The green substance at the surface of the 

 gonidium presents a peculiar granular or 

 globular appearance ; and it appears not far- 

 fetched to regard this body as composed of 

 a densely combined family of ordinary two- 

 or four-ciliated zoospores, such as would be 

 formed by the swarmiug-spores of Hydro - 

 dictyon if they remained in their primitive 

 crowded condition. This, however, is a point 

 requiring further examination. The end of 

 the tube from which the gonidium has 

 escaped appears as a hyaline sac (fig. 800), 

 which soon decays down to the point where 

 the contents parted, where a septum, now 

 closing the tube, is developed. 



After swimming about for some time, 

 fi'om one to several hours (usually about 

 two), the gonidium falls to the bottom of 

 the vessel, its cilia disappear, and it assumes 

 a spherical form, acquiring veiy soon a di- 

 stinct cellulose coat; after this it soon ger- 

 minates by pushing out one or more tubular 

 processes (tig. 802), which grow up into 



Fig. 802. 



Fig. 803. 



Vaucheria Ungeri. 



Fig. 802. Gonidia germinating. Magnified about 15 

 diameters. 



Fig. 803. Filament with gonidia germinating in the 

 parent tube ; the left-hand figure, half a divided goni- 

 dium. Magnified 25 diameters. 



filaments like the parent. Sometimes the 

 gonidium cannot make its escape, sometimes 

 half of it escapes and becomes pinched ofi^, 

 the other half being left behind; in these 

 cases, the arrested body, or the remainino- 

 portion of the divided one, germinates in 

 situ (fig. 803). 



It should be mentioned, that the contents 

 of the vegetative filaments have a remark- 

 able tenacity of life ; for if the tube is slightly 

 injured at any point, the primordial utricle 

 commonly retracts from the wound, and 

 secretes a cellulose layer on its surface, 

 shutting ofi" the injured part. Filaments are 



