202 THE MEDUSAE. 



necessary for the Panamic form, because of three features, — the presence of 

 an attenuated apical projection, the. fact that the gelatinous dome of the disc 

 is divided by a coronal furrow, and because the tentacles are swollenbasally 

 so as to form distinct bulbs, which is not the case, according to Ilaeckel's 

 figure ('79, taf. 4, fig. 10), in the West Indian S. lAerophijUa. Fortunately, I 

 have been able to test these three characters in a considerable series of Sto- 

 motoca in the present collection, from near the type locality of S. divisa, and 

 with the following results : — the presence of an apical projection proves to 

 be a character belonging to an immature state of development, and not one 

 diagnostic of the species ; for while it is present and more or less prominent 

 in small specimens, 15-20 mm. in diameter, it is entirely absent in the largest 

 specimens, which, not only from their size but also fi'om the condition of the 

 gonads, are evidently farther advanced tlian any examined by Maas. The 

 coronal furrow is present in some specimens (though in none very marked), 

 absent in others, apparently irrespective of stages in development, — a varia- 

 tion showing beyond question that the furrow is not in any way comparable, 

 with reference to constancy or systematic importance, to the coronal furrow 

 of the Coronata. None of the present specimens show such an extreme de- 

 velopment of the tentacular bases as Maas ('97, taf. 1, fig. S) has figured, yet 

 on the other hand there is always a definite thickening, so that in this re- 

 spect they stand intermediate between the accounts of Maas and Haeckel. 

 Inasmuch as the latter author drew his description solely from alcoholic 

 specimens it is a question how much stress to lay on this slight difference ; 

 for tentacles and even their bulbs often contract greatly, and even become 

 entirely distorted after preservation in alcohol. It is most unfortunate that 

 Haeckel could give no account of the color in 8. pterophylla, for from compari- 

 son with ^S*. atra it appears that this character may be of specific importance in 

 this genus. From the above facts it appears that the resemblance between 

 S. pterophi/Ua axid. 8. divisa is so close that it is doubtful whether the separation 

 of the two species is sound ; but since it is impossible to answer this ques- 

 tion definitely without a fresh study of West Indian specimens of S. pdero- 

 phi/lla, and since there is a possibility that the slight difference in the form 

 of the basal bulbs of the tentacles, and the occasional occurrence of a coronal 

 furrow in the Panamic form, may prove to distinguish it from 8. pterophi/lla, it 

 seems to me better to retain both names. 



8. atra, though closely allied to 8. pierophylla and 8. divisa, seems to be 

 characterized by a much darker coloration than that of the West Indian or 



