SEXUAL REPRODUCTION. 



169 



walls of the conceptacle in order to group themselves at the 

 centre, where they float in a watery fluid. These gonospheres 

 are then smooth and bare, with no membrane on their surface 

 of the nature of cellulose. 



During the formation of the oogonia there arise from its 

 pedicel or from neighbouring filaments slight cylindrical curved 

 branches, sometimes turned round the support of the oogonia, 

 and which all tend towards this organ. Their superior extremity 

 is intimately applied to ita wall, then ceases to be elongated, 

 becomes slightly inflated, and is limited below by a partition ; 

 it is then an oblong cell, slightly 

 curved, filled with protoplasm, and 

 intimately applied to the oogonia 

 in fact, an antheridium or organ of 

 the male sex. Each oogonium pos- 

 sesses one or several antheridia. 

 Towards the time when the gono- 

 spheres are formed it may be ob- 

 served that each antheridium sends 

 to the interior of the oogonia one 

 or several tubular processes, which 

 have crossed its side wall, and which 

 open at their extremity in order to 

 discharge their contents. These, racanosa.' (Cornu.7 

 while they are flowing out, present some very agile corpuscles, 

 and which, considering their resemblance to those in Vaucheria, 

 to which the name of spermatozoids are applied, ought to be 

 considered as the fecundating corpuscles. After the evacuation 

 of the antheridia the gonospheres are found to be covered with 

 cellulose ; they then constitute so many oospores, with solid 

 walls. De Bary considers that, bearing in mind analogous 

 phenomena observed in Vaucheria, and the direct observations 

 of Pringsheim,* the cellulose membrane on the surface of the 

 gonospheres is only the consequence of a sexual fecundation. 



In Achlya dioica the antheridium is cylindrical, the plasma 

 which it encloses is divided into particles, which attain nearly 

 * Pringsheim's " Jahrbucher," vol. ii. p. 169. 



FIG. 97. Conjugation in Achlya 



