into two equal parts. In the Closterium Lunula (fig. 57.), it is partly separated by sharp teeth; in other species, such as the Closterium spirale (fig. 67. h.), it appears like a green spiral ribbond in the cavity of the coat.
In the Pediastra, Euastra, Stauridia, Cosmaria and in the Colpopelta, the green substance fills entirely the two articulated parts of the animalcule, and hides often from one to four drops of oil (fig. 30. 31. 35. a. a.); but, near these drops, small solid and dark grains (b. b.) are seen swimming, and in a continual oscillatory motion, like the corpuscules of the rotatory vesicle of the Closteria. The same takes place in the Scenodesmi, Echinellae, Sphaerodesmi, etc.
In the Oscillatoriae the content consists in small disks, placed close one another, having only a small cavity, for ex. in the Oscillatoria labyrinthiformis (Pl. VI. fig. 76. a.).
ORGANS OF PROPAGATION.
The organs of generation are in this series very obscure and problematic. I do not know them. I shall however hazard a few observations, perhaps of some importance, which may he brought under this head, as long at least as we shall not be able to point out these organs more positively.
