THE ANNALS 
AND 
MAGAZINE OF NATURAL HISTORY, 
(SIXTH SERIES.] 
No. 21. SEPTEMBER 1889. 
XXI.—On the Organism of the Stphonophora and_ their 
Phylogenetic Derivation: a Criticism upon E. Haeckel’s 
so-called Medusome-theory. By Protessor CARL CLAusS*. 
AS is well known, opinions as to the interpretation of the 
Siphonophora diverge in two directions, a number of natu- 
ralists regarding them, after the example of C. Vogt and R. 
Leuckart, and in accordance with the latter’s theory of poly- 
morphism, as free-swimming Hydroid-stocks with Polypoid 
and Medusoid individuals, while other zoologists adhere to 
the older conception of Eschscholtz and Huxley, and, aided 
by the image of a proliferating Sarsia (Metschnikoff), refer 
the organism of the Siphonophore to the Medusa. I endea- 
voured, as long since as 1860 J, to demonstrate the correctness 
of the former view; but more recently, in two memoirs, I 
have pointed out what is common to the two theories and 
sought to combine them. The same thing has lately been 
done, although partly from other points of view, by Haeckel 
in his ‘ Report on the Siphonophore collected by H.M.S. 
‘Challenger’ during the years 1873-76,’ so rich in descrip- 
* Translated from a separate copy, furnished by the Author, of the 
memoir published in the ‘ Arbeiten des Zoologischen Instituts der Uni- 
versitat Wien,’ tom. viii. Heft ii. pp. 159-174 (1889). 
+ “Ueber Physophora hydrostatica,” in Zeitschy. f. wiss. Zool. Bd. xii, 
Ann. & Mag. N. Hist. Ser. 6. Vol. iv. 13 
