MUSEUM OF COMPARATIVE ZOOLOGY. 169 



of the ephyra. One of these is always in advance of the others in time of ap- 

 pearance, and is the longest. This predominance of one of these marginal ap- 

 pendages is another expression of bilateral symmetry, which, as has been pointed 

 out by others, is well marked in the tentacles in the younger scyphistoma stage 

 of Cyanea and Aureiia. 



In the ephyra in which there are eight tentacles on the margin of the um- 

 brella, octants of which I have represented, Plate VII. figs. 9, 10, the resem- 

 blance to the members of the family of Pelagidce is very striking. Not only in 

 the outward form is this likeness apparent, but in the internal anatomy the 

 resemblances are very close. One of the most striking of these anatomical like- 

 nesvses is to be seen in the course of the chymiferous tubes in the sense octants 

 of these two forms. If one will compare Fig. 9 with a sense sector of Pelagia 

 cyanella, he will find the tubes almost identical in their course. The addition 

 of new tentacles on the margin of the umbrella of the ephyra takes place by 

 the growth of new tentacles on either side of that first formed, and in pairs, one 

 on each side at the same time. These grow along two sides of a V-shaped 

 figure, in which the first formed tentacle is situated at the angle of the V, and 

 is directed towards the centre of the ephyra. The subsequently formed tenta- 

 cles to the primary always arise external to those already developed. Marginal 

 tentacles in all stages of growth, from a bud to a well-developed filament, ar- 

 ranged along the figure of which I have spoken, are shown in Plate VII. fig. 8. 

 The same figure shows also the changes which have taken place in the contour 

 of the rim of the sense octant, and the greater development of the bundle of 

 sexual tentacles. The specimen from which the drawing was made was not 

 raised from the larval ephyra, but was taken free swimming in the dip-net. 



In some of the older forms following the ephyra stage, the upper surface of 

 the umbrella is covered with peculiar undescribed filaments. These are well 

 shown in a young Cyanea somewhat older than that, an octant of which 

 is figured, Plate VII. fig. 7. This stage with the filamentous appendages is 

 shown, Plate VII. fig. 1. The whole upper surface of the umbrella is covered 

 with peculiar tentacles of unknown function. They are most developed in 

 younger stages, but are not wholly wanting in the adult. The filaments to 

 which I refer were first noticed in these young Cyanem by Dr. Walter Faxon. 

 Of the anatomy of these filaments there is very little to be said. They are 

 very flexible, transparent, of brownish color, tapering uniformly from base to 

 extremity, and seem to be simple prolongations of the substance of the bell, 

 covered by a layer resembling that which is stretched over the whole of the 

 aboral surface of the umbrella. They are also solid, and destitute of lasso-cells. 

 Their superficial layer is penetrated by those same nerve cells which are found 

 all over the surface of the umbrella, the histology of which has been so elabo- 

 rately investigated by Dr. Eimer. These cells are undoubtedly connected with 

 sensation of some special kind, and we may consider with great probability that 

 the aboral filaments are specialized sense organs. I suggest for them, whatever 

 their function may be, the name of " aboral papillae." In some genera of Dis- 

 cophorcB the same appendages also exist, but they are nowhere as prominent as 



