36 Some Aspects of the At gee. 
that Karsten’s recent discovery of numerous gametes in the Plankton 
diatom Corethron, makes many of his (Oltmanns’) conclusions 
“again doubtful,” and we cannot but think that the origin of both 
the Diatoms and Conjugates is still wrapped in profound mystery. 
With the remarks on the Volvocales and Protococcales we are 
in close agreement. The treatment of Ulotrichales and Chaeto- 
phoraceae reveals nothing very new; the possibility of deriving the 
peculiar zoospore of (Edogonium from the bi-flagellate type is 
discussed and the fact that the two flagella of such a zoospore as 
that of Cladopliora are not really terminal, but arise on each side 
of a terminal papilla, is brought in evidence. The Chaetophoraceae 
and allied families are derived, as usual, from the Ulotrichaceous 
type, but their treatment here is decidedly meagre. 
The Siphonocladiales are derived from uninucleate cell-types 
such as the Ulotrichaceae by division of the nucleus, rather than by 
the septation of the Siphoneous plant, while the Siphoneae proper, it 
is suggested may have arisen from the Siphonocladiales by sup¬ 
pression of thesepta, through the Codiaceae. The Siphonocladiales 
are also thought to have given rise to the Verticillatae, through 
Dasycladns, and to the Caulerpaceae, through C. fastigiata, so that 
the septate coenocytic group would thus become the common 
ancestors of the whole of the Siphonoideae. 
This possibility cannot be altogether neglected, but the line of 
evolution indicated involves a wholesale reduction of structure 
which necessitates rather an unwieldy hypothesis, and one scarcely 
to be adopted without more cogent arguments than are adduced. 
We prefer to adhere for the present to the simpler hypothesis of 
the evolution of the Siphoneae from the Protococcales through a 
form like Protosiphon, since the “siphoneous tendency” is clearly 
indicated within the latter group. 
Professor Oltmanns is evidently not altogether satisfied with 
the position of Vauclieria as belonging to the Siphoneae, though he 
suggests a comparison with Codium ; neither is he quite willing to 
accept Bohlin’s view. The position of Vauclieria must remain still 
very doubtful. 
The old-fashioned view of the connexion of the Rhodophyceae 
(from which the Bangialesare altogether excluded, as more naturally 
placed with Prasiolaceae) with Coleochaete does not find much 
favour in Professor Oltmanns’ eyes, and in this we certainly 
sympathise. But he inclines to the opinion, especially on the ground 
of the striking parallelism of their “sporophytes,” that the Florideae 
