Organism of the 8iphonophora. 189 



organisms, now to be designated as Siplionopliora (" lloliren- 

 quallen"), which acquire the character of Hjdroid-stocks, 

 would not, as the preceding remarks have shown, be in the 

 least degree contradicted ; but rather their appendages, 

 according as they repeat the stomachal pediiucle (polypites) 

 or the Medusan umbrella, and relatively both segments in a 

 simplified form (sexual buds), would be now as before charac- 

 terizable as Polypoid and Medusoid individuals in Leuckart's 

 sense. But as we have already ascertained that the Poli/pe 

 and Medusa are fundamentally one and the same *, the differ- 

 ence expressed in the two conceptions loould be of significance 

 only with regard to the phylogenetic relations of the Siphono- 

 phora. 



" Moreover it is evident, as may also be deduced in the 

 same way from the morphology and developmental history of 

 the Cestodea, that the ideas of the individual and animal- 

 stock in the lower animals are by no means morphologically 

 sharply defined and opposed to each other in Haeckcl's sense 

 of '■ person ' and ' cormus,' but must be regarded ordy as 

 relative ideas in the same way as those of ' organ ' and 

 ^ individual,' and vary in their application according to the 

 objects compared. Therefore, also, Leuckart's criterion^ lohich 

 is supposed to prove the individuality of all the Siphonophoran 

 appendages, namely their similarity of constitution in the hud- 

 state, cannot in this sense he in the least degree accepted. By 

 it the marginal filaments of the Medusan umbrella, the ten- 

 tacles of a Scyphistoma, or of any polyp would also be shown 

 to be individuals. This certainly unmistakable contradiction, 

 which, however, is at once got rid of by the conception of the 

 individual and stock as relative ideas, appears to have been 

 Metsehnikoff's principal inducement to oppose the theory of 

 polymorphism and, so to speak, empty out the baby with the 

 bath." 



In the subsequent smaller paper I expressed myself no less 

 definitely (p. 9) upon the relation of the two views and the pos- 

 sibility of combining them as follows : — " I have already (in 

 the memoir on Halistemma) endeavoured to show that the 

 difference between the two conceptions, especially considering 

 the relative value of the idea ' Individual ' and the relation of 

 the Medusa to the Hydroid-stock as the sexual animal pro- 

 duced by the latter, is by no means so considerable as it 

 seems to be at the first glance, and that even the second con- 



* 111 a previous passage of the same memoir (pp. 2G-30) the morpho- 

 lugical derivation of the nectocalvx, Hydroid Medusa, and Acalepli from 

 polypes was <^eneticall.v established. 



