548 E. T. GUNTHEK. 



of the gonads. Hence the Leptomedussa and the Tracho- 

 medusse are the only two sub-orders which can be considered. 

 Allman (4) enrolled Limnocodium among the Leptomedusae 

 on the erroneous assumption that the sense-organs were entirely 

 derived from the ectoderm of the velum. This, however, was 

 shown not to be the case by Ray Lankester (2), who proved their 

 partial eudodermic origin, and accordingly transferred the me- 

 dusa to the ranks of the Trachomedusae. This change he, more- 

 over, supported by pointing out that Limnocodium resembles 

 the Trachomedusae in certain other respects. On the other hand, 

 it has been urged, and I think justly, that Limnocodium has a 

 fixed hydroid stage, a thing which is quite unknown among 

 Trachomedusae, and certainly absent in some of them. In my 

 own opinion, to include Limnocodium among the Tracho- 

 medusae in the present state of our knowledge cannot but 

 render that group an unnatural one, or more unnatural than 

 it is at present. On the other hand, it cannot be denied that 

 Limnocodium has reached a Trachomedusan grade of develop- 

 ment in the possession of sense-organs with an endodermal 

 axis. Limnocodium, then, is a medusa descended from Lepto- 

 medusan ancestors, which has developed sense-organs with an 

 endodermal axis independently of the Trachomedusae. 



List of Authors referred to in Text. 



1. 0. and R. Hertwig. — 'Organismus der Medusen,' Jena, 1878. 



2. E, Ray Lankester. — "Limnocodium Sowerbii," 'Quart. Journ. 



Micr. Sci.,' xx, 1880. 



3. E. Ray Lankester.—" On the Intra-cellular Digestion and Endoderm of 



Limnocodium," 'Quart. Journ, Micr. Sci.,' xxi, 1881. 



4. G. J. Allman. — "Limnocodium victoria," 'Journ. Linn. Soc.,' xv, 



188L 



5. A. de Varenne. — ' Recherches sur les polypes hydraires,' Paris, 1882. 



6. J. Thallwitz. — " tjber die Entwickelung der mannlicben Keimzellen bei 



den Hydroideen," ' Jen. Zeitschr. f. Nat.,' xviii, 1885. 



7. G. H. Fowler. — "Hydroid Phase of Limnocodium Sowerbyi," 



' Quart. Journ, Micr. Sci.,' xxx, 1890. 



