312 QUARTERLY CHRONICLE OF MICROSCOPICAL;SCIENCE. 
organs he identified with the hairs which line the bladders 
found on the fronds, but which, as Mirbel pointed out are 
nothing more than the débris of cellular tissue. 
Fucus will always have a special interest in the history of 
these researches. It was the first alga in which the actual 
phenomenon of the fertilization of the oosphere, by the 
incorporation with it of the antherozoids, was ever witnessed. 
Thuret’s observations on the subject were communicated to 
the Académie des Sciences in 1853. ‘The peculiarity of the 
Fucacee is that both oospheres and antherozoids are set free, 
which is to a certain extent a return to the form of conjuga- 
tion met with in Pandorina. The contents of the oogonium 
form from one to eight oospheres, which are naked masses 
of protoplasm destitute of motile organs. The antherozoids 
collect about them in such numbers as to impart to them a 
movement of rotation (fig. 9). 
Fie. 9.—Fertilization of Fucus. a, antherozoids x 330; 4, oosphere sur- 
rounded by antherozoids x 160 (after Thuret). 
In a memoir on Volvox which Cohn has lately privately 
published as a Festschrift in honour of Prof. Goppert, he has 
remarked that the agreement of all the sexual relations of 
Volvoz and Eudorina with Spheroplea on the one hand, and 
with Fucus on the other, is so clear that the distribution of 
these alge in two different classes must appear unnatural, 
and the position of all the genera named amongst the 
Oosporee cannot be doubted. 
It will, no doubt, seem a grave objection to a classification 
that it requires the breaking up of a group apparently so 
natural as Volvocinee as generally limited. The progressive 
morphological differentiation of the members of that group 
cannot fail to be apparent and to suggest their close genetic 
connection. 
But it must now be clear that Sachs’s classes have no strict 
genetic signification, and only mark and measure grades of 
development. We must still, therefore, attempt to arrange 
our groups in genetic linear series independently of it. These 
will be vertical, and will be intersected by the horizontal 
boundaries of Sachs’s classes. 
Pu mOsPOREH.—Sachs suggests as a provisional arrange- 
