SEXUAL REPRODUCTION OF THALLOPHYTES, 3ll 
eight remaining or female cells (oogonia)...... to the capsules 
of which they apply themselves most vigorously and perti- 
naceously, flattening, elongating and changing themselves 
into various forms as they glide over their surfaces, until they 
find a point of ingress, when they appear to slip in, and, 
coming in contact with the female cell, to sink into her sub- 
stance as by amalgamation.”) 
In Volvox antheridia and oogonia are, as in Eudorina, found 
in the same colony, which is then moneecious, or they are found 
exclusively in different colonies, which are therefore dicecious. 
The sexual cells exhibit a further degree of specialization, 
inasmuch as only a small proportion of the cells of a colony 
are developed into them. The oospheres are conspicuous by 
their large size, and are surrounded by a gelatinous cell-wall 
(oogonium). ‘This is penetrated by the antherozoids when 
they escape from the antheridia (fig. 8). 
Fie. 8.—Fertilization of Volvor. a, antherozoid x 800; 4, oogonium with 
antherozoids penetrating the gelatinous cell-wall x 400 (after Cohn). 
SpH#RoPLEA.—If we are compelled to divorce Eudorina 
and Volvox from the Pandorinee we are equally obliged to 
separate on the same grounds Spheroplea from its conferva- 
ceous allies. The contents of the cells of this filamentous 
alga, instead of forming microzoospores, develope into 
oospheres and antherozoids. ‘These are formed in different 
filaments, and the antherozoids being set free find their way 
through apertures in the walls of the oogonial cells and 
fertilize the oospheres. 
Fucacrem.—As early as 1711, what we now know to be 
the organs of reproduction of Fucus were discovered by 
Réaumur. He observed the orange-red exudation from the 
openings of the conceptacles which Decaisne and Thuret 
(1845) showed to consist of a mass of antheridia containing 
antherozoids. Linnzeus with tolerable accuracy described as 
the ‘ feminei flores” of Fucus the club-shaped ends of the 
branches of the frond or vesicule, as he termed them, 
*‘ adspersee punctis perforatis semine feetis.” The male 
1 Ann. Nat. Hist.,’ 3rd ser., ii, 1858, pp. 239, 240. 
