Dr. F. Cohn on a new genus of the family of Volvocinea). 407 



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

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

 other Algae and Infusoria exhibit a different behaviour towards 

 the lights 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 Btephanosphcerm from ChlamydococcuSy 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 : — 



■^k. 



AlGtM, 



Order Palmellace^e. [Chamcephycece, Kiitz.) 



Family Volvocine^. 



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



Stephanoma? Werneck, according to Ehrenberg's paper m 

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

 April 1846). 



Trichogonium ? Ehrenb. /. eod. 



Stephanosphcera in Eabenhorst's 'Algen Sachsens/ Bee. xi. 

 No. 102. 



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

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

 cilia, 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 oifour cilia, and then escaping singly. 



Spec. Char. — Stephanosphaei-a pluvialis, n. s. Green cells glo- 

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

 at both ends. Diameter of the cells = 33^Qth to y^oth of a line 

 (0*0065 to 0*012 mm.) ; diameter of common vesicle = ^\jth to 

 ^^th 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, JVerneckh Zambra, A. von 

 Frantzius ; Hirschberg, Von Flotow. 



The principal results of my investigations may be pretty ac- 

 curately comprised in the following statements : — 



1. Stephanosphcera 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. 



