THE GONOfHORES OF THE HyDROCOtlALLlN^. 195 



importance by themselves to justify the separation of the Hydro- 

 corallinse from the Hydromedusee. 



Lankester (9) places them in a separate order of the sub- 

 class HydromedusEe. 



In the classification used at Cambridge Balfour placed 

 Millepora and the Stylasteridse in the sub-order Hydroidea 

 of the order Hydromedusse. 



Glaus, in his ' Grundzuge der Zoologie/ makes the Hydro- 

 corallinse the first sub-order of the order Hydromedusee. 



In Jackson's edition of RoUeston's ' Forms of Animal Life ' 

 (8) the order Hydroidea is divided into the three sub-orders 

 (1) Tubularise, (2) HydrocoralliuEe, and (3) Campanularise. 



The opinion I have come to, based upon Moseley's researches 

 and my own, is that the Hydrocorallinae should be placed in 

 an order apart from tlie Tubularise and Campanularise (i.e. 

 Hydroidea of Balfour and Jackson). 



The classification of the Hydrocorallinae with the Hydroidea 

 was perfectly justified by the state of knowledge at the time. 

 Both dimorphism and skeletal structures are, comparatively 

 speaking, uncertain features for the purposes of classification, 

 and the character and structure of the polyps and their con- 

 necting canal systems show undoubted affinities with many 

 forms of Tubularise. 



Unless, then, the organs that bear the sexual products can 

 be shown to differ very widely from those of the Hydroidea, 

 and present characteristics peculiarly their own, the Hydro- 

 corallinae must remain in the position that is assigned to them 

 by some authorities in the order Hydroidea. 



These considerations demand a careful and exhaustive com- 

 parison of the typical gonophores of the Tubularise, and of those 

 Hydrocorallines that are at present known to us. 



To aid in the discussion of the homologies I have given on 

 p. 390 diagrammatic figures representing the structure of 

 (Woodcut 2) a phanerocodonic medusa, (3) a medusa of Mille- 

 pora, (4) an adelocodonic medusa, (5) the male gonophore of 

 Allopora, (6) the male gonophore of Distich opora, (7) the 

 female gonophore of Distichopora. 



