ALGAE. CONJUGATAE. 51 



into symmetrical halves (X), and are also compressed perpendicularly to the plane of con- 

 striction (7, a). In each symmetrical lobe are two amylum-bodies and eight chlorophyll- 

 plates, which curve and converge in pairs and run from two points of union to the wall. 

 In cell-multiplication the narrowest part of the constriction elongates a little, while the 

 external thicker layer of the cell-wall opens by a circular fissure. Then the two lobes 

 of the cell appear to have moved apart from one another and to be connected by a 

 short canal, whose wall is a continuation o the inner layer of the cell- wall of the two 

 lobes. Soon a transverse wall appears in the connecting canal, which divides the cell 

 into two daughter-cells, each of which is a half of the mother-cell. The transverse wall, 

 at first simple, now separates into two lamellae, which at once become convex towards 

 one another (IX, //). Each daughter-cell now possesses a small convex outgrowth 

 which increases in size and takes the form of a cell-lobe, so that each daughter-cell is 

 now composed of two symmetrical lobes (X). While the wall thus grows, the 

 chlorophyll-body of the older lobe also grows out into the new lobe. The two amylum- 

 bodies of the old cell-lobes elongate, become constricted, and divide each into two 

 bodies ; two of the four bodies pass over into the new lobes, and all four arrange 



FIG. 28. Cosmdrinm- Bot'rytis. I III inagn. 390 times, lVX 190 times. After be Bary. 



themselves in the former symmetrical manner. Conjugation takes place between pairs 

 of cells, which lie cross-wise enclosed in a thin jelly (/). Each of the two cells puts 

 out from its centre towards the other a conjugating process (7, c\ and the two processes 

 meet and touch ; they are clothed with a delicate membrane, a continuation of *he 

 inner layer of the cell-wall, the firm outer layer haviiig burst asunder (/, c}. The two 

 processes expand each into a hemispherical bladder arid touch one another ; the wall that 

 separates them disappears, the contents unite in the broad canal thus formed, and the 

 protoplasm separates entirely from the cell-wall and contracts into a spherical body, 

 which now appears invested with a delicate gelatinous membrane (77, /) ; by its side 

 lie the empty cell- walls (77, e> &). The zygospore is now a found ball, and as it ripens 

 its cell-wall is differentiated into three layers, an outer and an inner colourless layer of 

 cellulose, and a middle layer which is firmer and brown. This stratified cell-wall now 

 forms spinous processes at several points on its surface, which are at first hollow, after- 

 wards solid, and each of them produces a few smaller teeth at its extremity (777). The 

 starch-grains of the conjugated cells change in the zygospore into fatty substances. 

 At the commencement of germination the colourless inner layer of the cell-wall protrudes 



E 2 



