Dr. F. Cobn on a new genus of the family of Volvociueas. 407 



part of the vessel, avoiding however a total absence of light and as- 

 sembling in preference in a moderated light or half-shadoiv. Since 

 other Algae and Infusoria exhibit a different behaviour towards 

 the light, we thus possess a means of sorting, to a certain extent, 

 the microscopic inhabitants of a specimen of water, as I did the 

 shade-loving Stephanosplujerte from Chlamydococcus, which ordi- 

 narily seek the brightest light. 



X. Summary of the Results. 



I conclude my essay with the diagnosis of the new genus 

 which has formed its subject : — 



Alg^. 



Order Palmellace^. (Chamc^hT/cea, Kiitz.) 



Family Volvocine^. 



Stephanosphara, nov. gen. (Wreath-globe.) 



Stephanoma ? Werneck, according to Ehrenberg's paper in 

 'Gesellsch. naturforsch. Freunde^ (Spenersche Zeitung,vol. xxviii. 

 April 1846). 



Trichogonium ? Ehrenb. /. eod. 



Stephanosphara in Rabenhorst's ' Algen Sachsens/ Dec. xi. 

 No. 102. 



Gen. Char. — A family of cells, rotating and moving throughout 

 life ; composed of eight green primordial-cells, bearing two active 

 (iilia, arranged at equal distances in a circle passing round, en- 

 closed in a common, hyaline, globose vesicle; propagated both 

 by macrogonidia originating from eightfold division of each of the 

 green cells, and bearing two cilia, congregated into eight octo- 

 nary families, and very numerous smaller microgonidia, produced 

 by multifold division, turning round first within the common 

 vesicle by the action of four cilia, and then escaping singly. 



Spec. Char. — Stephannsp/mra jiluvialis, n. s. Green cells glo- 

 bose, elliptical or fusiform, often running out into mucous rays 

 at both ends. Diameter of the cells = 3yQth to y^oth of a line 

 (0"0065 to 0-012 mm.) ; diameter of common vesicle = ^^^th to 

 .f^oth of a line (0-028 to 0055 mm.). 



Obs. Revives after desiccation. 



Inhabits hollow stones filled with rain-water, in company with 

 Chlamydococcus pluvialis '. Salzburg, Werneckl. Zambra, A. von 

 Frantzius ; Hirschberg, Von Flotow. 



The principal results of my investigations may be pretty ac- 

 curately comprised in the following statements : — 



1 . Stephanosphara is a new genus of the group of Volvocinea, 

 and only essentially differs from Pandorina, Gonium and Volvox 

 through the law of arrangement of the internal green globes. 



