ALGAE. VOLVOCINEAE. 



37 



Eudorina elegans l , a species resembling Pandorina in appearance in many of the 

 stages of its development, shows very great advance in the differentiation of the sexual 

 elements. The coenobia are hollow bodies of ellipsoidal form with 16-32 (rarely only 

 8) cells enclosed in a common gelatinous envelope ; each cell has two long cilia which 

 protrude a long distance through holes in the envelope, a red eye-spot, and, in all the 

 specimens which I have examined, a hyaline anterior extremity which is often rostrate. 

 The plant multiplies itself copiously in the asexual manner, new coenobia being formed 

 from the cells of the old ones, as in Pandorina. The cell-wall first swells up and sepa- 

 rates from the protoplasm, which first divides into two parts, and then into four by a 

 wall at right angles to the first. The young colony is next seen to separate into eight 

 cells (Fig. 17, <:), which are so disposed that the four middle ones form a cross ; this 

 arises from the circumstance that the walls of the quadrants are a little curved, and an 

 anticlinal wall makes its appearance in each quadrant. Cells are then cut off from the 



FIG. 18. Eudorina elegans. I. a female colony (coenobium). The walls between the several cells are swollen into a jelly. Each 

 of the cells has two cilia, but they are not all visible. M 1 ,M 2 , M 3 male coenobia ; MI has just reached the female colony and caught 

 its cilia in it, Af 2 reached it earlier and its spermatozoids are separating from one another, Ms has broken up into the separate sper- 

 matozoids, which are forcing their way into the gelatinous envelope of the female colony to lay themselves upon its cells (Sp. sper- 

 matozoids). //. mother-cell of a male colony ; the swollen cell-wall is lifted off from the protoplasm ; A outer surface of the crenobium, 

 r red eye-spot, v contractile vacuole. ///. a young male coenobium seen sideways, consisting of a cell-disk, the cells of which have 

 been increased in number in V, VI. a mature male coenobium consisting of a bundle of spermatozoids, arranged like a bundle of 

 cigars ; each spermatozoid has two cilia at its extremity. The male coenobium is still enclosed in the swollen wall of the mother-cell, 

 but is just setting itself in motion ; it is subsequently set at liberty. IV. a young male colony seen from below. 



outer side of the 'cross-cells ' by periclinal walls, as is shown in Fig. 17, d, while the 

 four inner cells do not again divide. In this way a disk of cells is formed, the same 

 arrangement of cells therefore which the coenobia of the genus Gonium present all their 



1 The following statements rest on observations made in 1878, and they agree entirely with the 

 report on Goroshankin's Russian treatise (See Jahresbericht, 1875, p. 28), with the exception of 

 some unimportant details. 



