9] JOURNAL OF THE 
of the bell (on the floor of the sensory niche). They con- 
verge and unite, forming a superficial nerve tract which 
crosses the base of the sense-club. These four isolated 
tracts are regarded by Claus as the remnants of a once con- 
tinuous exumbrellar ring, such as is found in the Hydro- 
medusae. and which here, as in the Hydromedusae, stands 
in connection with the subumbrellar ring through the 
medium of fibres that perforate the jelly. Conant, on the 
other hand, regards the tracts lying across the bases of 
the sense organs as portions ef the primitive subumbrel- 
lar ring which were shut off from the main ring, when. 
the marginal lobes grew together. With the Hertwigs 
and Haeckei he thus looks on the ring as not homologous 
with that of the Craspedota, but as a special differentia- 
tion of the subumbrellar plexus found throughout the 
Scy phomedusae. 
The sense organs of the Cubomedusae are ‘sense-clubs’ 
or modified tentacles. In addition to the crystalline sac, 
the expanded head of the club bears six eyes. Four of 
these are simple, but two are complex organs provided 
witha cellular lens and cornea, a vitreous body behind 
the lens, anda retina. These eyes look into the bell cav- 
ity. Itis especially in reference to the structure of the 
retina and vitreous body of the complex eyes, that Co- 
nant’s conclusions differ from those of Schewiakoff. The 
vitreous body Conant finds is not a homogeneous struct- 
ure, butis composed of prisms of refracting substance. 
The retina does not show the two types of cells (sensory 
and pigmented) distinguished by Schewiakoff. Conant’s 
results in this matter of the retinal structure are in some 
respects negative. The points still to be cleared up are 
as in the case of the nerve cord, such as will require the 
free use of macerations and surface preparations of fresh 
tissue. 
