42 SEAWEEDS 
both within definite conceptacles more or less local- 
ised on the thallus, the oospheres being enormously 
greater in volume than the antherozoids. The 
antherozoids are at most sixty-four in each anther- 
idium, while the oospheres are typically eight in 
each oogonium. In particular genera each oogonium 
develops only one, or two, or four oospheres, but in 
all the Fucacew that have been examined in this 
respect the original nucleus of the oogonium always 
divides into eight daughter-nuclei, of which only 
those remain effective that are destined to belong to 
oospheres, while the remainder, in genera possessing 
one, two, or four oospheres, are rejected. Both an- 
therozoids and oospheres are extruded from the con- 
ceptacles, and fertilisation takes place, as in the rest 
of the Phwophyceee, outside the plant. There are no 
non-sexual spores produced, and with the exception of 
vegetative propagation by broken off fronds, there 
is no other kind of reproduction known in Fucacee. 
It is probable that in the parasitic and much 
reduced Notheia, of which research has failed to 
disclose the antheridia, the oospheres remain un- 
fertilised, and if they reproduce the plant, as is ex- 
tremely probable, do so parthenogenetically. Of all 
Algze they show the highest degree of differentiation 
of parts, and attain the greatest dimensions, with the 
single exception of the Laminariacee. A consider- 
able variation, however, occurs among the different 
genera in the matter of vegetative development, 
the least of any being exhibited by Notheia. 
The Thallus——The thallus of the Fucacee some- 
times attains a development and differentiation of 
