Notes on Medusa: of the Western Atlantic. 137 



tacles transparent, except for pattern of opaque white markings caused by 

 parasitic protozoa. 



Habitat. Very limited ; not found, so far as recorded, outside the moat of 

 Fort Jefferson, Tortugas Islands, except, perhaps, in a single case. (A speci- 

 men of Cladonema was taken by Dr. C. O. Whitman in 1883 on the shoals 

 near Fleming's Key, north of Key West, Florida. This was described by 

 Fewkes, 1 and from the similarity between this specimen and our species in 

 point of arrangement of canals it is not at all unlikely that it may be the 

 same. The other points of anatomy are not so clear, and there are no 

 figures.) Living in shallow water, close to the bottom, amongst tangled 

 masses of filamentous algae. 



II. THE HYDROID STAGE. 



CLADONEMA Hincks. 2 British Hydroid Zoophytes, 1868. 

 STAURIDIUM Dujardin. Ann. des Sci., 1843. 



Generic characters. Minute Stauridium-\ike hydroid arising from a 

 creeping stolon attached to alga, stone, or other supporting substance. In- 

 vested by a perisarc. Hydranth club-shaped, tapering from above down- 

 ward. Oral extremity rounded into a hypostome. Two series or verticils 

 of tentacles, a capitate set at the oral end, four in number, forming a cross, 

 thickly set with nematocysts ; at a distance down the column a second ver- 

 ticil of four stiff, rod-like tentacles, set opposite the angles between the 



upper set. 



Cladonema mayeri, new species. 



Specific characters. There does not appear to be any great difference be- 

 tween the various species of Cladonema, in the hydroid stage. Its consti- 

 tution is so simple in comparison with that of the rather complicated medusa 

 form that it is not surprising to find fewer points of contrast between 

 representatives of different species. Like Stauridium, Coryne, and Clava?- 

 tella, this genus offers a direct contrast to such hydrozoa as Obelia, in which 

 it is hard to recognize any differences between gonosomes which develop 

 upon trophosomes of very distinct character. The minute proportions of 

 the hydroid under discussion, the absence of tactile hairs on the tips of 



1 Fewkes, J. W. 1883. On a few Medusas from the Bermudas. Bull. Mus. Comp. 

 Zool. Harv. Col., xi, p. 87. 



2 I am aware that the name Stauridium has the authority of older usage. In fact 

 it was this name that was originally applied to the hydroid " nurse " of the free- 

 swimming Cladonema found by Dujardin in his aquarium. It is unfortunate that it 

 did not appeal to this astute naturalist as a convenient and permissible practice to 

 call two stages in the development of the same animal by the same name. Had there 

 not arisen confusion in the application of the name which Dujardin gave to his hydroid, 

 to other similar but not identical forms, it might be best to continue to use two dif- 

 ferent names for the medusa stage and the hydroid stage of the animal in question. 

 The old name has, however, been applied (Haeckel : System der Medusen) to hydroids 

 whose progeny are not Cladonema, but Sarsia. It is certainly desirable to simplify 

 our nomenclature to the utmost. I have thought that in this case it was by far 

 the better plan to follow Hincks in his very logical decision in the matter. 



