250 



PART IV. CLASSIFICATION. 



set free. 



~b 



The spermatozoids of Volvox are club-shaped, yellow, and 



bear two cilia, inserted 

 ' . laterally. 



Series III. SIPHO- 

 NOIDEJE. The forms in- 

 cluded in this series 

 may be arranged in 

 the three following 

 orders : Siphonacese, 

 Cladophoracese, Hy- 

 drodictyacese. 



Order 1. Siphona- 

 ceae. The body is an 

 unseptate coenocyte, 

 septa being only 

 formed in connexion 

 with the development 

 of reproductive or- 

 gans , it is usually 

 attached, and presents 

 a considerable variety 

 FIG. 139. Volvox Globator (after Cohn: *x about 100), of form; it may be 

 monoecious, with antheridia a, and oogonia b. thalloid and then be 



FIG. 140. Vaucheria smttix (x30): A sp a newly-formed zoogonidium; B a resting 

 zoospore ; C, the commencement, D and E more advanced stages, of germination ; 

 sj> zoospore ; apex of the green filament ; ic a colourless adventitious root ; F filament 

 with sexual organs; og oogonium ; h autheridium after rupture. (After Sachs.) 



