THE A.NNALS 

 MAGAZINE OF NATURAL HISTORY. 



[SECOND SERIES.] 

 No. 60. DECEMBER 1852. 



XXXVIII. — On a new Genvs of the Family o/Volvocinese. 

 By Dr. Ferdinand Cohn of Breslau. 



[Concluded from p. 347.] 



VIII. Comparison of the Development of Stephanosphsera with 

 the Formation of Swarming-cells in the other Alg<E. 



Whoever has observed the active spores {gonidia) of certain 

 Algae which are formed by the division of a primordial utricle in 

 the interior of a parent-cell, and after the rupture of the latter 

 emerge into the water by the help of moving cilia, will at once 

 perceive the perfect agreement of this phsenomenon with the 

 facts observed in the development of StephanosphtBra. The for- 

 mation and evacuation of the swarming-spores, as I have ob- 

 served it myself many times in Achlya proUfera, Chytridium, and 

 Conferva glomerata, and others in Ascidium, Bryopsis, Codium, 

 Ectocarpus, and the Fucoidese, presents the exhibition of swarm- 

 ing and streaming out exactly as we have just described it in the 

 rnicrogonidia of Stephanosphcera. The swarming-spores of Bry- 

 opsis, Chcetophora, Stigeoclonium, Ulothrix and Draparnaldia have 

 such a complete agreement of form with those of Stephanosphcera, 

 that it would not be possible to distinguish them if they were 

 seen only singly and not at the moment of emerging from the 

 parent-cell. All these spores of Algse bear four cilia at the an- 

 terior extremity, like the rnicrogonidia of Stephanosphcera ; a con- 

 dition which has not hitherto been observed in any true or 

 pseudo-Infusorium. Other swarming-cells have exactly similar 

 form, development and motion, but bear only two cilia, as in 

 those of Cladophora, Characium, Apiocystis, Phycoseris, Chceto- 

 morpha and others. The treatise of G. Thuret on the moving 

 spores of the Algse (Ann. des Sc. Nat. 3 serie, tom. xiv. 1850) 

 Ann. ^ Mag. N. Hist. Ser. 3. Vol.x. 26 



