260 
a critical representation of his Sertularian system, and in oider 
to make it more coherent and easier to read, I shall give most of 
the quotations, on which it is based, as notes. Schneider at 
first States 1 ) that my system, which is based on diversities in the 
opercular apparatus, cannot in any way stand together with that 
of the former authors who divide the genera mainly according to 
the arrangement of the liydrothecae in the branches 2 ). He admits 
that at first sight it looks seductive 3 ), but though he does not 
seem to have subjected it to a real test, he comes to the result 
that the oider authors are right in the main, and that such a 
great systematic importance cannot be ascribed to the opeiculum 
in opposition to the characters formerly used 4 ). — Schneider 
gives three reasons why he has not been able to admit my syste- 
matic characters. The first is connected with my assertion that 
there exists a certain harmony between the margin of the hydio- 
theca and the structure of the operculum, and that we, therefore, 
even in colonies which have lost their opercula, may be able from 
the structure of the former to draw a conclusion as to the charactei 
of the latter. Schneider thinks it possible, therefore, that a great 
deal of my statements are only based on this form of investi- 
gation 5 ), in which he evidently has no confidence. Howe\er, I 
q ,,Levinsen begrundet auf den Bau des Opercularapparats seine von 
der åltern durchaus abweichende Systematik. Es ist nothwendig, zu 
dieser sofort Stellung zu nekmen; denn, falis wir sie acceptiren mussen 
ist eine Besprechung der fruhern systematischen Angaben uberfiiissig 
ja unmoglick“ (p. 520). 
2 ) „Die åltere Systematik hielt sich, wenigstens in der Hauptsache, ar 
die Yertheilung der Hydrotheken an den Sympodien“ (p. 521). 
3 ) „Fur den ersten Blick hat diese Eintheilung etwas Bestechendes 
(p. 521). 
4 ) „Indessen fragt es sich, ob wir der Deckelbeschaffenheit so hoh< 
Bedeutung gegeniiber den bis jetzt angenommenen Charakteren zu 
schreiben durfen und ob letztere nicht doch wenigstens in den Haupt 
ziigen zu Reckt bestanden. Ich glaube nun, mich dieser letzterei 
Anschauung zuneigen zu mussen“ (p. 520). 
5 ) „Ueberhaupt mag Levinsen in den Auftkeilungen wohl oft zu seh 
der åusseren Besckaffenkeit der Hydrotkekenmiindung, die meist doc. 
nicht immer auf eine bestimmte Deckelbeschaffenheit schliessen låssi 
Rechnung getragen kaben“ (p. 522). 
