600 



MEDUSAE OF THE WOULD. 



lappets adjacent to the 16 rhopalar lappets are fully twice as wide as the others and are rarely 

 cleft. The actual number of marginal lappets is quite variable, but we may say that there are 

 typically 96 primary lappets, of which 48 are typically cleft. Counting these clefts we would 

 then have 18 lappets per ociant or 144 in all. The bell-margin usually bends at right angles 

 to the general surface of the exumbrella; subumbrella surface convex. 



Arm-disk octangular with re-entrant angles and sharply set off from subumbrella. It 

 is thick and about as wide as radius of bell. Thus in a medusa 168 mm. in diameter the arm- 

 disk was 88 mm. wide. 4 simple, small, oval, subgenital ostia on interradial sides of arm-disk 

 are not much wider than the width of a marginal lappet. The 8 adradial mouth-arms are 

 bluntly simitar-shaped in general outline, are laterally compressed, and only about half as 



FIG. 410. Cot\lorhiza tubfrculata, from life, by the author, at Naples Zoological Station, December, 1907. 



A, oral view with all but one of the mouth-arms removed. The muscular layer is also removed 

 over the area on to left side of the figure in order to show the canal-system. B, section 

 through medusa showing central stomach and unitary subgenital space below it. C, cross- 

 section through subgenital space (sparsely dotted) and stomach (with thickly placed linear 

 dots); showing the 8 ostia of the mouth-arm canals. D, mouth-arm cut off from arm-disk 

 and viewed from cut end. E, club-like appendages among the frilled mouths. F, sense- 

 organ seen from exumbrella side. 



long as bell-radius. They are somewhat thicker (downward) than wide and arise from the 

 arm-disk at 45 apart. Thus in a medusa 168 mm. in diameter the mouth-arms were each 

 46 mm. long and 54 mm. thick. Each mouth-arm bifurcates near its base and each of the two 

 main branches gives rise to about 10 to 14 side branches, which in turn give off 30 to 40 smaller 

 branches, and these again to 100 to 150 smaller branches, which branch still further dendritic- 

 ally. The farther out the branches the more dendritic and the less dichotomous is their mode 

 of branching. 



A large number of short, club-shaped appendages between the frilled mouths terminate 

 in bluntly conical to flatly expanded, disk-like ends covered with small, wart-like tubercles. 



