Appendix to Hydractinia. 



283 



generative one) having only one function, cannot be homo- 

 logous with one composed of two subelements (peduncle of 

 Sarsia), each having its distinct function, or with an organ 

 of sixteen subelements (peduncle of Bougainvillea), eight 

 of which are alimentary and eight reproductive. I would 

 therefore now state — 



That the simple generative sac of Coryne is homologous 

 with the reproductive subelement or single generative sac 

 as it exists on the lateral canal of Stomobrachium. 



That the peduncle-like sac of Eudendrium confertum is 

 homologous with the reproductive subelement in the pe- 

 duncle of Sarsia — not with the whole peduncle. 



That where the generative sac evidently consists of many 

 subelements, as in Tubidaria larynx and. Serhdaria fallax 

 (evidenced by the four summit-lips or lobes, the symmetri- 

 cal character of each of which indicates it to be composed of 

 two subelements), it is homologous with the reproductive 

 subelements in the octopartite peduncle of Bougainvillea, 

 or, rather, with the eight coalescing reproductive subele- 

 ments of Eleutlieria. 



I consider that a four-lobed or branched state of the pla- 

 centa or spadix indicates a multipartite constitution of the 

 generative sac, and not a rudimentary meclusoid form of that 

 organ ; for we have, in the fixed female medusoid of Lao- 

 medea Loveni, a four-lobed condition of the placenta in the 

 peduncle-like ovisac, with the existence of a well-differen- 

 tiated subumbrella and lateral and circular canals. 



My space will not allow me to illustrate the homological 

 relations which exist between the polypary (or coenosarc) 

 and the polypidom on the one hand, and the subumbrella 

 and umbrella on the other. This must be reserved for a 

 future occasion, when I hope to fill up the gaps in this 

 rough and incomplete sketch of some of the morphological 

 relations of the Hydroidse and their Medusae. 



Appendix to Hydractinia, printed at vol. i. p. 192. 



In the " Annals of Natural History " (vol. iv. ser. 3. p. 50) 

 Prof. Ailman has remarked, with regard to Hydractinia, 

 that " the solid chitinous polypary [polypidom] is covered 



VOL. II. 2 o 



