Organism of the Siphonophora. 191 
of assertions are posited as axioms and adopted as established 
propositions in the schematization of the new Medusome- 
theory. 
How does Haeckel prove to us that the primary Medusiform 
Siphonophoran larva is to be interpreted palingenetically, 
and demonstrate the truth of the assumption of an extensive 
multiplication and dislocation of the individual organs of the 
Medusa? And to what new factual conditions does he appeal 
when, as arbitrator in this main question, he rejects as erro- 
neous the opposite view, which denies a far-reaching secondary 
multiplication and dislocation of these organs, and regards 
the primary Medusiform larva as a cenogenetic form? Or is 
it more than an axiom to start from a bilateral Medusa as the 
primary larva or ‘‘siphonula,”’ which, distinguished by a 
ventral umbrellar fissure and the possession of a single mar- 
ginal filament, has originated from a primeval bilateral stem- 
form of the Anthomedusan group, to be christened “ Proto- 
meda”’? How long, in Hiickel’s system, has the bilateral 
symmetry, which, according to his Gastrea-theory, is pro- 
duced as a consequence of a creeping mode of life, been thus 
a primitive character of the Medusa, the ontogenetic develop- 
ment of which on the Hydroid-stock would indicate a regular 
radiate fundamental form ? 
By such a dogmatic assertion, at variance with all obser- 
vation, we certainly escape answering the question * in what 
manner the stomachal tube and tentacles have passed from 
the centre and the umbrellar margin to the outside of the 
Medusan umbrella, and what advantage this deviation from 
the radiate fundamental form could have had for the main- 
tenance of the organism, but without considering that in this 
way the knot has been cut and not loosened. 
It is the same with the second axiom, which gives Haeckel’s 
Medusa-theory its special character, namely the assumption of 
a second primitive stem-form of octoradial structure of the 
Trachymedusan group, called the “ Archimeda,” in order to 
derive therefrom a second Medusiform larva, the ‘‘ Disconula,”’ 
which, in possession of a marginal circlet of tentacles, has 
produced the individuals of the stock by gemmation from the 
subumbrella, and formed the starting-point for the develop- 
ment of the Discoidea (Porpita, Velella), rechristened Disco- 
nanthe. By this hypothesis and the supposition involved in 
it of a diphyletic origin of the Siphonophora, Haeckel’s theory 
certainly beomes a new variety of the Medusa-theory, but at 
the same time it loses probability in the same degree that the 
* See Claus, “‘ Ueber das Verhaltniss von Monophyes zur den Diphyiden 
&c.,” in Arbeiten des Zool. Instituts &c. (Vienna, 1885), p. 9. 
