5/2 MICEOSCOPIC FORMS OF VEGETABLE LIFE-THALLOPHYTES 



they precisely resemble the mature oospores which we have taken as 

 the starting-point in this curious history. Certain of the cells (as 

 in No. 14), instead of giving origin to oospores, have their annular 

 collections of endochrome converted into antherozoids, which, as 

 soon as they have disengaged themselves from the mucilaginous 

 sheath that envelopes them, move about rapidly in the cavity of their 

 containing cell (a, 6) around the large vacuoles which occupy its 

 interior, and then make their escape through apertures (c, d) which 

 form themselves in its wall, to find their way through similar aper- 

 tures into the interior of the oogones, as already described. These 

 antherozoids are shown in No. 15, as they appear when swimming 

 actively through the water by means of the two cilia which each 

 possesses. The peculiar interest of this history consists in the entire 

 absence of any special organs for the generative process, the ordinary 

 filamentous cell developing oospheres on the one hand and anthero- 

 zoids on the other, and in the simplicity of the means by which the 

 fecundating process is accomplished. 



The (Edogoniaceae resemble Confervacece in general aspect and 

 habit of life, but differ from them in some curious particulars. As 

 the component cells of the filaments extend themselves longitudi- 

 nally, new rings of cellulose are formed successively, and are inter- 

 calated into the cell-wall at its upper end, giving it a ringed appear- 

 ance. Only a single large zoospore is set free from each cell ; and 

 its liberation is accomplished by the almost complete fission of the 

 wall of the cell through one of these rings, a small part only remain- 

 ing uncleft, which serves as a kind of hinge whereby the two parts 

 of the filament are prevented from being altogether separated. 

 Sometimes the zoospore does not completely extricate itself from 

 the parent-cell ; and it may begin to grow in this situation, the 

 root-like processes which it puts forth being extended into the 

 cavity. The zoospores are the largest known in any class of algje ; 

 each has a nucleus, a red ' eye-spot,' and an anterior hyaline spot to 

 which is attached a tuft of cilia visible even before its escape from 

 its mother-cell. 



In their generative process, also, the (Edogoniacew show a curious 

 departure from the ordinary type ; for whilst the oospheres are 

 formed within certain dilated cells of the ordinary filament (fig. 432, 

 A, No. 1), which may be termed oogones, and are fertilised by the 

 penetration of antherozoids (No. 2), these antherozoids are not, in all 

 the species, the immediate product of the sperm-cells of the same or 

 of another filament, but are developed within a body termed an 

 androspore (No. 5), which is set free from within a special cell (No. 

 4), and which, being furnished with a terminal tuft of cilia, and having 

 motile powers, very strongly resembles an ordinary zoospore. This 

 androspore, after its period of activity has come to an end, attaches 

 itself to the outer surface of an oogone, or of a cell in close proxi- 

 mity to an oogone, as shown at No. 1, & ; it then developes into a 

 very small male plant, known as a dwarf -male, consisting of two or 

 three cells ; the terminal of these cells is an antherid, from the apex 

 of which a sort of lid drops, as seen in the upper part of No. 1, by 

 which its contained antherozoids (No. 2) are set free ; and at the 



