OONFERVOID ALGiE. 



267 



absent, or have not yet been observed ; when present, 

 they will be found projecting on one or both sides of 



Fig. 145. — Conferva. 



1, Volvox gldbator. 2, A section of volvox, showing the ciliated margin of the 

 cell 3, A portion more highly magnified, to show the young volvocina, with 

 their nuclei and thread-like attachments. 4, Spirogyra, near which are spores 

 in different stages of development. 5, Conferva floccosa. 6, Stigeoclonium 

 protensum, jointed filaments and single zoospores. 7, Staurocarpus gracilis, 

 conjugating filaments and spores. 



the filament, being somewhat longer than the latter. 

 Filaments inclosed in sheaths never, or but slightly, ex- 

 hibit their peculiar motion, although they may be seen 

 sliding in them, backwards and forwards, or leaving them 

 altogether. 



The filaments themselves have been supposed to consist 

 wholly of protoplasm ; this view, however, is scarcely 

 correct, since the protoplasm is enclosed in a cell-mem- 

 brane. The cellulin coat always shows cross-markings 

 corresponding to the striae when such are observable 



