186 Prof. Carl Claus on the 
tions of interesting and previously unknown forms, as also in 
a previously issued extract from this work *, in which he 
develops a mediatory theory, uniting, in the opinion of its 
author, the true constituents of the two older theories, whilst 
eliminating their errors, and for the first time revealing the 
true nature of the Siphonophora. 
Haeckel has very cleverly succeeded in giving an appearance 
of novelty and speciality to his “‘ Medusome-theory,” as he 
calls it, by placing in the foreground, in the definition of the 
two theories, certain subordinate points, and, in accordance 
with this, employing new designations which conceal the 
essence of the theories. The first is indicated as the poly- 
person theory, the second as the poly-organ theory ; and it is 
asserted of the two that they are still, as formerly, in absolute 
opposition to each other. According to the latter the Siphono- 
phore is a simple Hydromedusoid person, therefore a morpho- 
logical individual of the third order; while according to the 
other, which aftirms the derivation from polypes, it is a 
swimming hydropolyp stock or a morphological individual of 
the fourth order. Such a conception, however, by no means 
represents the true state of affairs, but is a one-sided represen- 
tation, obscuring the essence of the question, which, in the 
light of our notions as to the relation of Medusa and Polype, 
obtained by more recent investigations, must be regarded as 
incorrect. 
In accordance with these notions the theory of poly- 
morphism founded by Leuckart could by no means be sus- 
tained unaltered in its cld form and conception; and just as 
the supposed absolute opposition of poly-persons and _ poly- 
organs has long since been swept away, it is also no longer 
admissible to deduce from the reference of the Siphonophore 
toa swimming Hydroid stock ‘the philosophical corollary 
that the whole class sprang from Polypes.” 
Any one who is to some extent informed upon the subject 
of the Coelenterata will at once see that the theory which in 
the Siphonophore goes back to the Medusa, and which there- 
fore may perhaps be best designated the Medusa-theory, also 
by no means involves as a necessary conclusion that the 
Siphonophore is to be regarded as an individual of the third 
order in Haeckel’s sense. Jor, although the starting-form for 
the morphological formation of the larva is a Medusa from 
which, by continual gemmation of new Meduse or parts of 
Meduse, the appendages of the Siphonophore were deve- 
loped, the Siphonophore, in the same way as the Sarsta-stock 
* “System der Siphonophoren auf phylogenetischer Grundlage,” in 
Jenaische Zeitschr. f. Natuwrw. Bd. xxii. (1888). 
