The usual modes of multiplication of the Diatomaceæ are stated to be either division or conjugation. Facke however suspected, though he did not actually observe, a formation of spores or gonidia such as are found in many of the filamentous Confervoids. This method of reproduction I beheve I have seen in Synedra ulna. In the autumn of last year I found, amongst a growth of Spirogyræ and Oscillatoriæ, a number of unusually large specimens of Synedra, some of such magnitude as to be visible to the naked eye. They were active, and evidently in a state of vigorous growth.
In fig. 12 I have endeavoured to depict the various stages of sporidial growth: a shows a full-grown Synedra with the endochrome diffused throughout the frond; at b the endochrome is beginning to gather itself into a distinct mass; at c it has divided, and a portion is attached to each of the frustules, and a division into definite masses is commencing; at d this division is complete, the masses forming lenticular bodies; at e they have moved into pairs, so that their convex surfaces are in contact; in the next stage (f) each pair has united and formed an elliptical spore; at g the frustule has been ruptured, and the spores are escaping. The escaped spores were evidently held together by a hyaline substance, and exhibited the peculiar motion termed swarming; h, i, j, show different stages of growth of the young Synedræ, until, at k, a perfect siliceous deposit has been formed, and the young Diatom is ready to recommence the whole process so soon as its endochrome is sufficiently mature.
Volvocineæ.
1. Protococcus viridis, M. Dic., 3.
{{{1}}}„ vulgare.
2. Hæmatococcus sanguineus.
{{{1}}}„ binalis.
{{{1}}}„ murorum, H., lxxxi.
3. Volvox globator, M. Dic., 3.
4. Pandorina murorum, M. Dic, 45.
Hæmatococcus.—I have had a colony of this protophyte in my possession for two years. I first discovered it in a jar which happened to be standing in the rain and was half filled with water. By keeping water continually in the jar the supply of Hamatococcus has never failed. Mr. Hamilton, of Petane, also brought me a sample in the wool of a sheep.[1]
