268 NATTTRAL HISTORY SOCIETY OF DUBLIN. 



diate question, for, whether the " hornlets" (antheridia) actually inoscu- 

 late with the openings of the oogonia or not, the essential circumstance 

 seems to be the union of the contents of the two organs. I certainly 

 never have encountered any Vaucheria in which any such inosculation 

 of the two organs seemed to exist, and Pringsheim's account appears to 

 be the most trustworthy. 



Again, in Sphseroplea the cell-contents of the very long ordinary 

 joint of a particular filament become broken up into a number of 

 rounded germ- cells ; and the contents of another ordinary joint become 

 broken up into an innumerable number of little bi ciliated sub fusiform 

 spermatozoids, which latter find their way out of their parent cell, and 

 into the cavity of the joint which contains the germ-cells, through 

 lateral openings in each. The fertilized oospore eventually developes 

 two coats, the outer beset with spine-like extensions. Here the diffe- 

 rence in size and appearance between the germ- and sperm-cells is 

 less than in Yaucheria, whilst the resemblance of the parent cells in 

 which they originate is still greater, being in fact but two ordinary, in 

 no way previously specialized, joints of the filament.* 



In (Edogonium, varied as 'are the conditions between monoecious, 

 gynandrosporous, and dioecious, under which the essential elements con- 

 cerned in the reproduction present themselves, there seems to be still 

 less difference, on the whole, in form and size of the spermatozoid and 

 the oogonium themselves, than in the other cases adverted to. 



In (Edogonium curvum but one spermatozoid is formed in each an- 

 theridium cell, and, like the oospore, it is globular ; and although there 

 is a considerable difference in size between the two, in this respect they 

 much more nearly approach than in the previously cited cases — that is, 

 though of course equally physiologically distinct, they are more nearly 

 morphologically equivalent. In (Edogonium, Cleve has shown that the 

 oospore in germination produces, by segmentation of its contents, four 

 daughter- cells, which become ciliated, and swim away as zoospores to 

 reproduce the species ;f while for Bulbochaete, whose fructification is 

 gynandrosporous, Pringsheim had previously shown that here also four 

 daughter- cells are developed from the oospores, which become zoospores, 

 and reproduce the plant. J 



These, then, are unquestioned and unquestionable instances of a 

 true generative act. It would be useless, as regards the subject under 

 consideration, to travel out of Confervoidese for further illustrative 

 cases where a true reproduction is effected by spermatozoids and 

 oospores, because we should be unnecessarily receding in the system 

 from Conjugatse. 



* Cohn, " Berichte der Berl. Akad.," 1855 ; also " Ann. des Sciences Naturelles," 4 

 Ser. v., p. 187 ; and " Ann. Nat. Hist.," 2 Ser. viii., p. 81. 



.. f Cleve " Iakttagelser ofver den -hvilande (Edogoniums-sporens utveckling," in 

 " Ofversigt af Kongl. Vetenskabs Akademiens Forhandlingar," Stockholm, 1863, p. 247. 

 X Pringsheim, "Beitrage zurMorphologieund Systematik der Algen." in " Jabrbiicher 

 fur wissenschaftliche Botanik," Band i., p. 55. 



