458 Mr. E. T. Browne on the Medusce 



this revision as complete as possible I have briefly given the 

 characters of new species of Staurophora and Ptychogena. 



A cordylus is an organ of a well-marked character, and 

 when once recognized it is not likely to be mistaken for 

 anything else on the margin of the umbrella. It is quite 

 distinct from marginal bulbs and tubercles or sprouting 

 tentacles and cirri. Its shape varies slightly in different 

 genera, but it always has a clear translucent appearance, 

 without any coloration, and is free from nematocysts. It is 

 also without otoliths and such concretions as are generally 

 found in sense-organs. Its function, however, has not yet 

 been definitely found out, but it is generally regarded as a 

 sensory organ. The first adequate description of a cordylus 

 was given by Brooks (1895), to whom the sensory theory is 

 due. 



Hartlaub's positive statement (1897) that the cordyli of 

 Stauro-pJiora develop into tentacles led me to carefully examine 

 early and intermediate stages of Laodice. If cordyli are the 

 forerunners of tentacles one would naturally expect to see 

 them in the earliest stage or in the very early stages; but 

 they do not make their appearance until the IMedusa has at 

 least trebled the original number of its tentacles. 



After searching the margins of the umbrella of several 

 dozen young Laodice, I did find two specimens which showed 

 cordyli being converted into tentacles. They showed, how- 

 ever, an exception to the normal course of development of a 

 tentacle which needs an explanation. 



When there is ample room between two tentacles one finds 

 a cordylus, a cirrus, and a tentacular bud in a single row and 

 isolated from one another. The tentacular bud increases in 

 size until it becomes a bulb, from which sprouts out the 

 tentacle. Under this condition there is not the slightest 

 indication of a cordylus becoming converted into a tentacle. 

 The stalk of the cordylus arises direct from the margin of the 

 umbrella and does not touch the tentacular bulb. 



In most young specimens the interval between two tentacles 

 has frequently the appearance of being overcrowded, owing 

 to the marginal appendages developing faster than the margin 

 of the umbrella. The tentacular buds arise alongside of, or 

 even underneath, the stalk of a cordylus, so that a cordylus is 

 often seen on the side, or on the top, of a tentacular bulb. 

 One specimen was seen with a number of buds and bulbs with 

 tentacles developing ; each bulb had a cirrus on its outer side 

 and a cordylus on its inner side. It was evident that the 

 tentacular bud had forced its way up between the cirrus and 



