ClIAP. II. 



THE DIFFERENT RADIATA. 



47 



understood of the i-clations of Ilydroids and naked-eyed Mcdusoe to show tliat there 

 is a genetic connection between them all, and such an identity in the essential 

 structure of the Ilydroids on one side and the naked-eyed Medusa^ on the other, 

 that the view which represents the Hydroids as true Polyps must lie for ever 

 banished from our science. This would Ije none the less true even should it appear 

 that the genuine Polyps form part of a larger division, emliracing also the Hydroids 

 with the naked-eyed Medusa? ; for such a comprehensive division would still have 

 to be subdivided into secondary groups, no one of which could include at the same 

 time true Polyps and Hydroids, without conflicting with their natural affinities. 



A few more words upon the Sertularians and Camjianulariaus and their free 

 Medusa? will set this matter at rest. A sterile head of Campanularia {Fi(j. 10, 

 and 15 c d), which is so strictly homologous to Sertularia or Dynamena {F/V/. 18) 

 that a comparison between the two is superfluous, shows a bell-shaped body, in 

 every respect identical with that of a Tubularia or Hj^bocodon {F/V/. 11). It has 

 a row of feelers around its margin like the latter, only the feelers are more 

 active, and capable of being drawn in more completely. The floor stretched across 

 the wider part of the bell is open in the centre, where we find the oral aperture. 

 The only difference in these parts between Campanularia and Tubularia is, that the 

 centre of this floor rises, in Tubularia, in the shape of a proboscis, while in Cam- 

 panularia it may only be raised to a small extent, but is at the same time capable 



Fiff. 19. 



Fig. 20. 



Fig. 21. 



COEYNE MIKABILIS, Ag. 



Hydra with a Jledusa bud. The 

 buds when freed become Sarsiie. 

 See fig. 21. 



a Stem of the Hydra. — v Its club-shaped 

 body. — o Its mouth. — 1 1 Tentjiclea 

 scattered over the body. — d Medusa 

 bud. 



Medusa bud of 



CORYNE MIKABIUS, Ag. 



The bud represented here sepa- 

 rately, with its base of attachment 

 a ctit thi'ough, is younger than 

 that represented in its natural con- 

 nection in fig. 19 (/. The free 

 lledusa is represented Fig. 21, and 

 described as Sarsia mirahilis in the 

 Contributions to the Nat. Hist, of 

 the Acalephs. 



a Base of attachment to the Hydra 

 stock. — o Proboscis. — b Radiating 

 chymiferous tubes. — t Tentacles. 



The free Medusa, Sarsia, of 



COEY'KE MIRABILI.S, Ag. 

 I Proboscis. — 4 Vertical chymifero 

 tube. — c Circular tube. — e e D 

 phragm. — tt Tentacles. 



of greater expansion and contraction. There is in that respect no greater diiler- 

 ence between Campanularia and Tubularia as Hydroids, than between Sarsia {Figs. 

 19 d, 20, and 21) or Hybocodon {Figs. 12, 13, and 14) as naked-eyed Medusa? and 



