186 Prof. Carl Glaus 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 hrs " 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 affirms 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 old 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 

 to a 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 Siphono]Dhore 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 HaeckeFs sense. For, although the starting-form for 

 the morphological formation of the larva is a Medusa from 

 which, by continual gemmation of new Medusae or parts of 

 Medusa?, the appendages of the Siphonophore were deve- 

 loped, the Siphonophore, in the same way as the Sarsia-stock 



• " System der Siphonoplioren auf phylogenetischer Grundlage," in 

 Jenaische Zeitschr. f. Natmw. Bd. xxii. (1888). 



