SEXUAL REPRODUCTION OF THALLOPHYTES. 315 
genetic ; the spores in this case only differ from those which 
have been fertilized in germinating more rapidly. 
ANCYLISTEHZ.—This is a new group of aquatic parasites 
described by Pfitzer. See ‘Q.J.M.S.,’ 1874, p. 296. 
PERONOSPOREH.—This group of which the white rust 
of cabbages andothercultivated Cruciferae (Cystopus candidus) 
and the potato-disease (Peronospora infestans) are well- 
known representatives, was thoroughly investigated by De 
Bary! in 1863. The phenomena of fertilization closely re- 
semble those which take place in the Saprolegniacee. From 
the oospore of Cystopus antherozoids are produced which 
give rise to the sexual plant. 
CipoGoNIE# are a group of filamentous algze which in many 
respects are typical Oosporee. The oosphere is fertilised as in 
Vaucheria by antherozoids. Zoospores, oospheres, and anthe- 
rozoids are formed from the cells of the filament, an arrange- 
ment which is clearly not far removed from that which 
obtains in Confervacee the microzoospores of which are repre- 
Fic. 11.—Fertilization of @dogonium ciliatum. (1) Filament with two 
oogonia, the lower with two “dwarf males” attached, the upper with 
oosphere in process of fertilization by an antherozoid set free from its 
accompanying ‘“ dwarf male ;” (2) antherozoids ; (3) oogonium contain- 
ing oospore ; (4) filament discharging zoospore (5) ; (after Pringsheim.) 
sented here by non-motile oospheres and antherozoids. In 
1 «Ann, des Se. Nat.,’ 4e sér., tom. xx. 
