PHAOPHYCEA 59 
emitted by each sporangium.. While the thallus 
that bears these sporangia in Zanardinia is of the 
same structure as that which bears the antheridia 
and oogonia, it is otherwise, as has been said, in 
Cutleria. The young plants produced by the germ- 
inating zygote of Cutleria are wholly different from 
the upright thallus of the sexual generation, and 
these young plants have always proved sterile so far 
as cultivated specimens directly observed are con- 
cerned; but they apparently agree so well with the 
plants formerly known as species of Aglaozonia 
which do bear zoosporangia like those of Zanardinia, 
that 16 may be fairly concluded there is an alternation 
of generations between the sexual Cuéleria plants 
which never bear zoosporangia and the non-sexual 
Aglaczonia plants. 
There is a resemblance between the sori of anther- 
idia and oogonia in Cutleriacew and the sori of similar 
organs in Fucacee, situated though these are in con- 
ceptacles. Sometimes the oogonia of the Cutleriacex 
are terminal on unbranched hairs, while the 
antheridia are, at least those in the middle of the 
sori, more copiously branched. The oogonia on . 
branching hairs in Sarcophycus may be recalled 
for comparison, while the paraphyses in both 
orders are not unlike in many respects. The 
Cutleriacee are unique, however, so far as is known, 
in the possession of ciliated oospheres of greater 
size than the antherozoids (cf. Codiacew), but other- 
wise resembling them, and this cardinal fact points 
to relationship on the other hand with the orders of 
Pheeophycee in which the gametes are both motile, 
