THE EDWARDSIA-STAGE OE LEBEUNIA. 311 



vacuolated endoderm persistent in Eupliyllia and Eclwardsia just 

 mentioned recalls so strongly the conditions in the late larvse of 

 Lebrtmia, ttat it seems not improbable similar diverticula may 

 also have occurred in these species at an earlier stage in their 

 development. 



It is evident from all this, that in most Scyphozoa the forma- 

 tion of the gastro-coelomic cavity of the adult takes place at a 

 much earlier stage than in Lelrunia, so that probably no complete 

 and distinct larval coelomie system is ever formed. This in no 

 way disproves the view here presented. All that can be asserted 

 from the resume just given is that the disorganization to form 

 the secondary body-cavity usually originates at such an early 

 stage that no opportunity exists for the primary enteric and 

 coelomie system to establish itself. From such conditions as 

 those revealed by Lelrunia in fig. 15 (PI. 19), there seems no 

 reason why at some time a species may not be found in which the 

 archenteron is prolonged centrally beyond the origin of the 

 diverticula, in which case we should have a temporary digestive 

 cavity with closed walls. In this connection one is tempted to 

 recall the ramified digestive tract described by Bourne (1887) as 

 occurring in ISuphyllia. 



The larva of Lebrunia is in many respects of an exceptional 

 character. If the interpretation of its tetrameral primary 

 tentacles be correct, it shovps that phylogenetically it is, in 

 regard to these organs, at a stage earlier than other Zoantharian 

 larvse yet described, and perhaps the same may be said of much 

 of its internal condition. No doubt the two sets of phenomena 

 are in some way interdependent. 



VI. BiBLIOGEAPHY *. 



1860. DucHASsAiNG, P., et MiCHELOTTi, J. — " Memoiro sur les 

 Coralliaires des Antilles." Mem. della E-. Accad. Sci. 

 Torino, ser. II., xix. 



1879. Hertwig, O. & E. — ' Die Actinien.' Jena. 



1884. Maek, E. L. — " Selections from Embryological Mono- 

 graphs, III. Polyps." Mem. Mus. Comp. Zool., vol. ix. 



* "Under this heading I include only the few original works which, cut off 

 from any fuUy-equipped scientific Library, I have been able actually to consult. 



