THE GONOPHORES OF THE HVDROCORALLIN^. 195 



importance by themselves to justify the separation of the Hydro- 

 corallinse from the Hydromedusae. 



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

 class HydromedusK. 



In the classification used at Cambridge Balfour placed 

 Millepora and the Stylasteridae in the sub-order Hydroidea 

 of the order Hydromedusae. 



Claus, in his ' Grundzuge der Zoologie,' makes the Hydro- 

 corallinse the first sub-order of the order Hydromedusae. 



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

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

 (1) Tubularise, (2) Hydrocorallinse, 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 the Tubularise and Campanularise (i.e. 

 Hydroidea of Balfour and Jackson). 



The classification of the Hydrocorallinse 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 diff'er very widely from those of the Hydroidea, 

 and present characteristics peculiarly their own, the Hydro- 

 corallinse 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 Tubularias, and of those 

 Hydrocoral lines 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 Distichopora, (7) the 

 female gonophore of Distichopora. 



