Australian Hydroids 331 



From the foregoing account, and from Brock's figure, it is- 

 obvious that in the most impoitant feature — the form of the oral 

 portion of the hydranth — the species described agrees absolutely 

 with Silicularia luididafa and Orthopyris calicidafa, as I have 

 described them, and also with Jickeli's figure of the latter species. 

 The likeness is emphasized in the description of B. rtyia by 

 Nutting, who says that the " veloid " is dome-shaped, in which ic 

 agrees with the proboscis of the above-mentioned two species when 

 not expanded. 



We have therefore in Bonneviella and OrtJiojiyris precisely the 

 same structure of the oral region, except that in the one case the 

 proboscidial cavity is said to be lined with ectoderm, while in the 

 other the lining membrane is described as endodermal ; a difference 

 which could hardly be demonstrated in the absence of sections. For 

 it is recognized that in the ordinary Campanularian hydranth the 

 hypostome is lined witli a special endoderm, consisting of cylinder- 

 cells smaller and Avith smaller nuclei than those of the main body- 

 cavity (probably implying special functions), while Broch describes 

 the ectodermal lining of the distal cavity in Bonneviella as also 

 consisting of cylinder-epithelium. The thickening of the lining- 

 men^brane opposite the bases of the tentacles is equally noticeable in 

 Bonneviella and in Sdicularia, 



I have seen no sections, but on the authority of Jickeli I regard 

 the pioboscidial cavity of OrfJiopf/ris as a true endoderm-lined 

 hypostome, and the very close affinity existing between that genus 

 and Sdicularui seems to justify the ascription of the same character 

 to tlie latter. Tlie outstanding difference between the In'dranths 

 of tliese two genera is tlie unilateral inflation in Sdicnlaria, Avhiclr 

 is correlated with the remarkable form of the hydrothecae. 



A peculiarity of Bonne rielki is the structure of tlie endoderm of 

 the tentacles, the cells ])eing in several series, a feature which Broch: 

 says is not found elsewhei'e among tlix? Thecaphora.i 



Note on the name Orthopyxis. 



Di-. Fraser, in a recently-published paper,- advocates the use of 

 the name Eucopella in preference to Orthopyxis, on the ground 

 that Agassiz failed to indicate the special characters which inducetf 

 him to separate 0. calicidata from other Campanularians. I do- 



1 It may he iiot*<l that Stecliow does not accept IJroch's intPi|>retatioii of the oral striu-ture irv 

 Bonneviella, but coiiHi<lcrx that the fi;jure indicates the exinten<'e of a conical h.v|)Ontonu', hucIj as- 

 characterise* the Lafoeidae.— Hvdroidpolypeii der japanischen Os'kUst*', ii., 1013, p. 28. 



2 Hydroids of Ka>teiii ( anada. Ottawa, 191. «. 



