INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 891 



important homologies between the Ctenophora and the Meclusfe 

 (specially Cijdipiie and Ctenaria). 



Ctenophora. Craspedota (Cladonemida). 



1. Gastric cavity = Umbrella-cavity. 



2. Oral margin = Umbrella-margin. 



3. Iimer surface of gastric cavity . . = Subumbrella. 



4. Mouth of infundibulum .. .. = Primitive simple Medusa-moutli. 



5. The two lateral pouches for the) _ JThe two lateral pouches for the ton- 



teutacles j\ tacles found in some Cladonemida. 



6. The two lateral tentacles .. .. ={^^f, two lateral tentacles of somo 



\ Craspedota. 



7. The eight adradial " ctenophores " = T^^edSffi'''^''''^'''^ "°''' °^ '"""^ ^°*^°' 



It is also pointed out that the four primitive peri-radial canals of 

 the Ctenophora appear to be homologous with the four peri-radial 

 canals which are found permanently in the majority of the Craspedota; 

 the eight adradial canals of the Ctenophora, which are formed by the 

 division of the four peri-radial ones, are also to be found in some 

 Cladonemida ; while those pinnate branches, which are in the Cteno- 

 phora converted into genital glands, form either generative glands in 

 some Craspedota {Gonionemus, Ptychogena) or simple glands which 

 have no generative function (Catahlema, Ctenaria). 



Ctenaria ctenophora, which belongs to the family of the Cladonemida, 

 has an ovate umbrella provided on its outer surface (exumbrella) with 

 eight adradial meridional costce, which are jDrincipally made up of 

 rows of urticating cells, and these are the parts which are homologous 

 with the " ctenophores " of the Ctenoj)hora ; the subumbrella has its 

 musculature only feebly developed and passes into a delicate velum. 

 The gastric cavity is small and is separated by a constriction from a 

 large and pyriform apical cavity, which occupies the aboral third of 

 the umbrella ; this latter is homologous with the " infundibulum " of 

 tlie Ctenophora and with the " brood-cavity " of Eleutheria. The 

 mouth is surrounded by sixteen simple tentacles. Four simple and 

 hemisi^herical gonads (generative glands) lie in the wall of the gastric 

 cavity ; four short peri-radial canals arise from the constriction 

 between the gastric and a2)ical cavities and soon bifurcate to form 

 eight adradial canals which pass to the margin of the umbrella ; these 

 eight canals are provided with glandular diverticula and are con- 

 nected together, at the margin, by a circular canal; wdth this last 

 there are connected two peri-radial tentacles, which form two loner 

 hollow tubes, which are beset with a series of lateral filaments. From 

 these notes it will be gathered that although Ctenaria presents us 

 with nothing new, it unites in itself a number of characters, of which 

 a part only have been hitherto observed in any one genus of the 

 AnthomedussB ; thus it has, for example, the eight urticating costfe of 

 Ectopleura, the apical cavity of Eleutlieria, the gastric characters of 

 Cijtceis, the gastro-canal arrangement of Cladonema, and the pinnate 

 tentacles and tentacle-pouches of Gemmaria. 



After dealing with the important questions of the homologies 

 of the different parts in the Medusas and the Ctenophora, Professor 

 Haeckel comes to a consideration of the ontogeny and phylogeny 



