752 
ROBERT PAYNE BIGELOW 
of these genera is known, each genus in the course of its ontogeny 
recapitulates in each successive stage the condition which remains 
permanent in each of the lower genera. The lack of a single 
important break in the series of adult forms is remarkable, and 
in Palephyra and the yet simpler Ephyra are found structures 
that show relationship to still more primitive forms." It was 
my task to discover whether a study of the anatomy and develop- 
ment of the sense-organs would or would not confirm this general- 
ization. 
At the present day that point of view^ appears rather quaintly 
old-fashioned. Nevertheless it seems worth while to publish 
the paper because it contains an account of the anatomy and 
development of these interesting organs that is more complete 
than any hitherto published, so far as the species herein treated 
are concerned. And it seems especially appropriate that an 
article reflecting, as this one does, the thoughts and methods of 
Professor Brooks at the period of his greatest activity, should 
appear in the present volume . 
Since this paper was written the conditions of the problem have 
changed considerably. On the side of greater complexity a new 
genus, Kuragea, has been added by Kishinouye ('02), and on the 
other hand Vanhoffen ('02) suggests that Haeckel's genera Ephyra 
and Zonephyra are not phylogenetic but ontogenetic steps and 
he unites all three into the single genus Palephyra. 
Mayer^ has thrown similar doubt upon the mutual relation- 
ships of the genera Chrysoara, Dactylometra, and Kuragea. 
He thinks that the so-called Chrysaora of our coast is nothing 
more than an imperfectly developed Dactylometra. He retains 
the genus Chrysaora, however, for three imperfectly separable 
species, and my study of the sense-organs seems to indicate that 
the forms on our coast are really two species, and perhaps repre- 
sent two separate genera. 
Since 1890 our knowledge of the marginal sense-organs of the 
Scyphomedusae has been increased by Hesse's detailed descrip- 
^ I am greatly indebted to Dr. A. G. Mayer for the gift of a set of the proof sheets 
of his forthcoming work on the medusae and for permission to quote from them. 
