ORGANS OF REPRODUCTION. 



389 



formed apparently without any process of fertilization out of the 

 contents of the cells, and are discharged, according to Henfrej, 

 without any cellulose coat, but consist simply of a protoplasmic 

 sac. They are furnished with ciliee, by which they are enabled to 

 move fi-eely for some time, hence their name ; but they after- 

 wards settle down and germinate, when Jhey also acquire a cel- 

 lulose coat. The number of cilise varies in' dilFerent plants ; in 

 some there are two {fig. 14), in others four {fig. 829), in others 



Fig. 828. 



Fig. 830. 



Fig. 829. 



Fig. 828. Portions of two filaments of Zygnema conjugating, c, d. Tlie contents 

 (endochrome) of two cells mixing by means of a lateral process, p. s. Germinating 

 spore, which results from the imion and mixing of the contents. The two cells 



below contain spiral filaments Fig. 829. Zoospore of Choetophora, consisting of 



a cell, V, with four ciliae, c, at its apex Fig. 830. End of a filament of Vaucheria 



Ungeri, with a single gonidium or zoospore, g, escaping. 



there is a tuft of cilite at one end {fig. 15), while in others, again, 

 as in Vaucheria, the spores are ciliated all over {fig. 16). They 

 may be produced either singly in the cells, as in Vaucheria {fig. 

 830), or in great numbers, as in Achh/a {fig. 146); and they 

 ultimately escape by rupturing the coats of the cell in which they 

 are contained {figs. 830, g, and 146, b). 



Some Conferv^oids have two kinds of zoospores, which are 

 termed respectively, macrogonidia and microgonidia ; the latter 

 are smaller and longer than the former, and are thought by some 

 authors to resemble spermatozoids in their function. 



These zoospores are sometimes confounded with spermatozoids, 

 from which structures, however, they are quite distinct. Henfrey 

 has thus distinguished them- — "The essential character of a 

 zoospore is, that when separated from the parent it becomes en- 

 cysted, and at once developed into a new individual resembling 

 the parent, (certain obscure exceptions however occur, where 

 the zoospore after germinating, at once discharges new ciliated 

 bodies (zoospores or spermatozoids (?)). Spermatozoids are 

 C C 3 



