VOLVOX AND ITS ALLIES. 



245 



bury themselyes in the hyaline envelope, and finally pene- 

 trate and become fused into the oosphere {b, Fig. 164). A 

 thick wall now forms upon the fertilized oosphere, and it 

 becomes transformed into an oospore. Thus we have in 

 these plants the transformation of an 

 individual of the colony into an oogo- 

 nium and oosphere, and the subse- 

 quent fertilization of the latter by 

 spermatozoids, which are themselves 

 fractional parts of other members of 

 the colony. 



326. — The relationship of the low- 

 er Oosporese with the lower Zygo- 

 sporese, as indicated by Volvox and 

 Pandori'na, is further shown by the 

 position of SpJimroplea, an undoubted 

 relative of the Confervacem {Clado- 

 pJiora, etc.). Sphmroplea is a free, 

 unbranched, filamentous alga, com- 

 l^osed of long cells joined end to end 



{A, Fig. 165). It produces OOSphereS Unaf "'^''orlinary'mament^ 



in some of its filaments, each cell '^.iT'c^St^i'^' ooi^i 

 producing several (5, Fig. 165). ^^^^h^erf J:Topl,i'^|s'r 

 While these are forming in one set of «ntrance of Bpermatozoick ; 



,, ? «,«, spermatozoids enteniig the 



filaments, in another the protoplasm oogoniu ; m aud k, oospheres 



, , , . . 1,-, 1 at the mslant of fertilization; 



becomes broken up into a multitude », fertilized oosph.res, now 



of elongated, bi-ciliate spermatozoids flhTmeSt "onsiTttag^ of ™nthe?- 



{G and G, Fig. 165) ; these escape SzSk's, Lt i^J ?Cf gffi 



through lateral openings in the cells, Smgs o<.^ £'at?o°f°c&"" 



which are formed by the absorption '"^e. ^.zoospore (veget-nive 



„ , ,. •' , , , ^ . zoogonidmm). F, oosphere in 



of a part of the wall, and then swim- the act of being fertUized by'a 



, , 1 J.1 J. xi_ c 1 spermatozoid, s. G, spemiato- 



mmg through the water they find zoids.— After CErsted. 

 their way to corresponding openings in the walls of the 



and their allies in the Oosporese, and Pand irina and its allies in the 

 ZygoBporesB, be placed in a common class Zoosporeae. This class 

 would tlius have two branches, one in the division Zyjfosporeae, and 

 the other in the Oosporese. Such an arrangement would indicate 

 the evident relationship of the plants under consideration better than 

 any yet proposed. 



