73° 



LECTURE XLI. 



and are apparently also similarly constituted, and such sexual acts were named 

 Conjugation, in contrast to the ordinary acts of Fertilisation which exclusively occur 

 in Mosses and Vascular Cryptogams particularly, where the one of the two sexual 

 cells, relatively large and non-motile, functions as the Oosphere, and is fertilised by 

 a relatively very minute and actively moving zoosperm (antherozoid). The investi- 

 gations of late years, however, have brought to light numerous cases from which 

 it must be concluded that no essential diiference exists between conjugation and 

 ordinary fertilisation by means of antherozoids ; this may be concluded from the 

 fact, among others, that both forms of sexual process occur in very closely allied 

 species. Goebel found, for instance, in the case of one of the Volvocinese which is 



Fig. 4zs.~Eneiorifta elesans, a female colony (cosiiobiuin) around which antherozoids Si are swarming 



(after Goebel). 



closely allied to the Pandorina described above, and, like that, consists of a revolving 

 coenobium, that the sexual cells are differentiated into oospheres and relatively minute 

 antherozoids. The plant in question, Eudorina elegans, consists of gelatinous vesicles 

 of elliptical shape, in which are contained 1 6 or 32 cells, each of which possesses two 

 cilia, which project through holes in the envelope far into the surrounding water. 

 Active multiplication occurs by the asexual method, each individual cell of a famUy 

 becoming transformed by appropriate divisions into a family consisting of 16 or 

 32 cells again: these young families are set free by the disintegration of the parent 

 envelope. Sooner or later, however, a sexual difference makes its appearance 

 between different ccenobia : some become male, others female. In the latter, 16 or 

 32 cells assume the character of oospheres, not conspicuously different from ordinary 



