OF THE PHYTOZOA. 175 



in a short time all the corpuscles emitted from an envelope-cell are scattered 

 and disappear in the wide surface of the drop of water. 



''I have not been able to make out what becomes of the microgonidia 

 subsequently, since they are ordinarily decomposed on the object-holder after 

 a brief swarming ; but it may be conjectiu^ed that they also serve for propa- 

 gation, and probably pass into a condition of rest. At least the latter has 

 been observed in the microgonidia of Chlamydococcus pluvialis by Alex. Braun 

 and myself: the history of the development of the latter agrees wholly with 

 those of the Stephano splicer a ; they originate also by the di\'ision of the pri- 

 mordial cell in a higher power, are distinguished by their minute size and 

 more active, peculiarly Infusorioid movement, and never develope an envelope- 

 ceU duiing their movement. The microgonidia of both therefore are true 

 primordial cells ; that is, primordial utricles resembling cells, organized ex- 

 clusively of coloured protoplasm, without any cellular membrane. The only 

 distinction between them is, that the microgonidia of Chlamydococcus, like 

 their macrogonidia, possess two cHia, while in those of StephanospJicera I 

 observed four. That the microgonidia of Stephanosphcera correspond per- 

 fectly in moi'phological respects to the macrogonidia, and only depend upon a 

 higher power of division, is proved by a case in which seven out of the eight 

 primordial cells in one envelope-cell were broken up into microgonidia, while 

 one divided merely into eiglit secondary cells ; the latter were developed as 

 macrogonidia, and formed a connected wreath suiTounded by an envelope-cell, 

 which rolled slowly about in the parent- envelope, suzTOunded by the swarm 

 of fi'ee, rapidly moving microgonidia. 



" Abstracting the differences which may be shown always between two 

 genera, we detect the same law of development in Hydrodictyon as m Stepha- 

 nosphcera, — viz. the bicHiated less numerous macrogonidia arrange them- 

 selves into a family of cells abeady "within the parent-cell, according to the 

 character of the given conditions of the two genera, the cell-family being 

 active in the Volvocineoe and immoveable in the Protococcacece, while the 

 more numerous more actively moving microgonidia with foui' cHia leave the 

 parent-cell and enter upon a metamorphosis, the retrogradation from which 

 to the normal type of the genus has not been observed yet here, or indeed in 

 the microgonidia of any of the Algae. Such an mideniable agreement of the 

 law of development of Stephanosphct^ra with an undoubted plant like Hydro- 

 dictyon, which testifies to a near relationship, would be inconceivable if the 

 former were to be regarded as of essentially different organization — as belong- 

 ing to quite another kingdom of nature. Thus the developmental history of 

 Stephanosphcera also fiu'nishcs the most convincing proof of the vegetable 

 nature of this genus, and consequently of the Volvocineoe generally. 



" That the formation of macro- and microgonidia does not exhaust the 

 whole series of forms which Steplianosphcera may pass through, is proved by 

 the following observation, which unfortunately I have not yet been able to 

 complete. Having cultivated some Stephanospliaerce for a long time in a little 

 glass cup, in the way described in my essay on Loxodes bursaria (7. c), all 

 the primordial cells at length exhibited dark, thick, greenish brown contents, 

 so densely filled with numerous granules that the two chlorophyll-vesicles 

 could no longer be detected ; their form was more or less globular, and the 

 mucous radiating processes were entirely absent ; their outlines were remark- 

 ably sharply defined, as if they had become suiTounded by a rigid membrane. 

 At the same time I remarked that the primordial cells were no longer fixed 

 immoveably at the periphery of the envelope cell, never changing their relative 

 positions, but jerked backwards and forwards, finally tore themselves away 

 from the envelope -cell, and then began to rotate slowly and lazily in the interior. 



