178 THE VOYAGE OF H.M.S. CHALLENGER. 



Ocean. They differ in size and form, and especially in the shape of the basal face and the 

 ventral sinus, more or less from the Mediterranean species, but were not sufficient for 

 the definition of distinct species. To enable this, a further accurate examination and 

 comparison of the entire corm, from different localities, is required. 



The most accurate description of the Mediterranean Hippopodius gleba ^Hippo- 

 podius luteus, Vogt, 6, very common on the Riviera) is given by Leuckart. 1 It differs 

 somewhat from similar forms taken in other parts of the Mediterranean. That form 

 which Kolliker has described as Hippopodius neapolitanus from Messina ( = Elephantopus 

 neapolitanus, Lesson, 3) seems to belong to the following genus, Polyphyes. The mouth 

 of the nectosac is surrounded in the latter by six prominent teeth (four dorsal and two 

 ventral), whilst it is smooth and toothless in Hippopodius. Another important difference 

 between these two genera seems to be found in the composition of the cormidia. The 

 clustered gonophores are diclinic, and attached to the base of the siphon in Hippopodius, 

 whilst they are monoclinic and separated from it by a small interval in Polyphyes. 

 Both genera together make up the subfamily Hippopodidae. 



The striking contradictions between various authors, respecting the sexual organs of 

 Hippopodius, can be explained only by the assumption that these two similar genera 

 have been confounded. The description which Leuckart has given of the diclinic 

 cormidia of Hippopodius gleba (8) is as correct as that which Kolliker has given of the 

 monoclinic cormidia of Hippopodius neapolitanus (4). The accuracy of these latter 

 observations has been confirmed recently also by Weismann, in his work on Die 

 Entstehung der Sexual-Zellen bei den Hydromedusen (1883, p. 194). He found in 

 each cormidium associated a single female and two male gonophores. Perhaps these 

 differences in the composition of the cormidia of the two genera are more important 

 than those in the form of their nectophores. 



Germs 34. Polyphyes, 2 Haeckel, 1888. 

 Polyphyes, Hkl., System der Siphonophoren, p. 36. 



Definition. — Polyphyidas with rounded horseshoe-shaped nectophores, the ostium of 

 which is surrounded by six prominent apophyses. (Cormidia monoclinic. Gonophores 

 separated from the base of the siphons.) 



The genus Polyphyes differs from the preceding closely allied Hippopodius as well 

 in the form of the nectophores as in the composition of the cormidia. The nectophores 

 have in general the same horseshoe-shape as in Hippopodius ; but in this latter their 

 dorsal face is equally convex and smooth, and passes over into the lateral faces without 

 a sharp edge. In Polyphyes their dorsal face is nearly quadrangular, and separated by 

 two lateral parallel smooth edges from the lateral faces ; further, the basal edge of their 



1 8, pp. 299-309, Taf. xii. figs. 1-4. 2 Polyphyes = Animal with numerous buds, ■no^vipvris. 



