314 RHODALIIDAE. 



ingenious suggestion that the aurophore represents the modified distal portion 

 of the pneumatophore, {. e. the pneumatosaccus, instead of corresponding to the 

 pneumatochone, and that the voknninous portion of the pneumatophore repre- 

 sents the latter. This view has been violently attacked by Schneider ('98). 

 Meanwhile, though all these students agree that the aurophore was not the 

 unique structure Haeckel supposed, the explanation given by the latter found 

 its way into most text-books. Such, in brief, was the history of the subject up 

 to 1908, when Lens and Van Riemsdijk published their very valuable researches 

 on Archangelopsis, from which they were able to demonstrate that the auro- 

 phore differs in no essential anatomical feature from the pneumatochone of 

 Physophora. So close is the agreement between the two, and so entirely is 

 it corroborated by the aurophore in Dromalia and in Angelopsis, that I think 

 no doubt can longer remain that the two structures, aurophore and pneuma- 

 tochone, are homologous. It does not seem to me, however, that their remodeling 

 (:08, p. 99) of Haeckel's longitudinal section ('88b, pi. 5, fig. 24) of the aurophore 

 of Rhodalia is altogether sound. No doubt his representation of a central canal 

 traversing the pneumatochone ("pistillum") and connecting the cavity of the 

 pneumatosaccus with the exterior via the aurophore, represents nothing more 

 than the spherical cavities so common in the secondary ectoderm both of 

 Archangelopsis and of Dromalia. But it is by no means certain that the 

 "porus" in Rhodalia is accidental. On the contrary, although there was no 

 connection between it and pneumatochone (the supposed junction in Haeckel's 

 figure being a portion of one of the septa) the condition in Dromalia where the 

 papillae all open by terminal pores, suggests that Haeckel observed a true excre- 

 tory pore opening into that portion of the pericystic cavity which is enclosed 

 within the aurophore. Furthermore, in view of the fact that the aurophore 

 is smooth walled in Angelopsis, it is unnecessary to assume that it possessed 

 papillae or appendages of any sort in Rhodalia. It is not likely that Haeckel 

 would have overlooked structures so prominent as the papillae, especially when 

 Lens and Van Riemsdijk themselves found (:08, p. 91) that his material, now 

 in the British Museum, is still fairl^y well preserved. Furthermore we can 

 hardly assume that papillae would later develop, because the large size of the 

 "Challenger" specimens of Rhodalia (60 mm. in diameter) and the advanced 

 condition of their gonophores show that they were mature. 



The authors just mentioned have also sharply criticised Haeckel's descrip- 

 tion and figures of a zone of proliferation lying opposite the aurophore. And 

 since this question is imjiortant we must examine the validity of their arguments. 



