208 THE PHENOMENON OF 



grandchildren), which begin to move soon after they arc 

 completely formed, and, tearing open the delicate en- 

 veloping vesicle, part company. The whole of this 

 process of development is gone through very rapidly, 

 being completed in one night and the succeeding 

 morning. The second active generation, thus formed, 

 resembles the first, with the single distinction that the 

 active cells are green from the first, and have a smaller 

 red nucleus in the interior. The subsequent active 

 generations bear a general resemblance to the preceding, 

 but many modifications present themselves. Thus, for 

 example, we not unfrequently see the full-grown swarm- 

 cells assume strange two-lobed, or even four-lobed, shapes, 

 beginning to divide before they come to rest ; or some- 

 times a transverse construction and bisection of the cell 

 takes place, caused by a partial protrusion of it from the 

 loose shirt, &c. The formation of cavities (Vacuoles) is a 

 pretty constant phenomenon in the later active gene- 

 rations, and there may be several of them eccentrically 

 placed, with the red nucleus retaining its central position, 

 or a single central vacuole, causing a lateral displacement 

 of the red nucleus. If water-cavities of this kind displace 

 the green mucilaginous layer entirely, in places, so that 

 they come in contact with the primordial utricle, the 

 form is produced which Von Flotow called Hamatococcus 

 plumalis Zacunosus, and has represented in pi. 25, figs. 

 69 and 70, loc. cit. The red nucleus often becomes very 

 small in the last generations, so that it very much 

 resembles, especially when rendered parietal by the 

 formation of a central vacuole, the red corpuscle occurring 

 in the gonidia of many genera of Algae, belonging to 

 very diverse families, and which was called the " eye", in 

 the Volvocineae, by Ehrenberg.* 



* I have observed an "eye" of this kind in the swarming gonidia of 

 Hydrodictyon, Ulothrix zonata, (vide Kiitz., ' Phye. gen.,' t. Ixxx,) Uloth. 

 Braunii, K., Hormidium variabile, K., Draparnatdia, Stigeoclonium, (in 

 several species,) Chalophora, (likewise many,) Coleochate pulvinata, Cludo- 

 phora glomerata; therefore in genera belonging to five different families, not 



