SENSE-ORGANS IN MEDUSAE 
769 
Except the endodermal lamella, there are no cellular elements 
imbedded in the mesogloea in the neighborhood of the sense- organ 
in either of the three species under consideration. There are 
many fibers in the mesogloea, especially in Dactylometra, but 
they are apparently only connective tissue fibers serving to give 
firmness or elasticity to the jelly and there is no evidence that 
the> have any connection with the nervous system. Schafer and 
SchewiakofT both speak of the connection between the layer of 
nerve fibers in the dorsal sensory groove and the nerve fibers in the 
niche, and Hesse finds in Rhizostoma fibers extending from the 
fundus of the dorsal sensory groove to the endoderm of the 
rhopalial canal, and he regards these as nerve fibers, in spite of 
the fact that they would not stain with methylene blue or gold 
chloride. If there is such a connection in the Pelagidae it is not 
through the mesogloea. In fact, the mesogloea immediately 
surrounding the sensor> groove in Dactylometra seems to be 
perfectly structureless, although the fibers are so well developed 
in other parts of it. 
SOME LARVAL STAGES OF DACTYLOMETRA 
The questions that now remain to be answered in this paper 
concern the stages in the development of Dactylometra. Unfor- 
tunately my material for this purpoes is very scant. 
The youngest of some larvae taken near Newport that I sup- 
pose to be Dactylometra is a little less than 2 mm. broad. It has 
four gastric filaments, the tentacles are just budding and the 
tentacular pouches of the stomach are about half as long as the 
rhopalial ones, while from the latter the marginal pockets are 
beginning to grow into the ephyra lobes. This specimen may, 
therefore, be regarded as on the border line between the Ephyra- 
and the Palephyra-stage. Sections of the rhopalium, fig. 35, show 
little differences between this and the slightly earlier stage of 
Chrysaora that I have already described. The constriction at 
the end of the rhopaUal canal is less marked and the distal part 
of the rhopalium may be relatively a little longer. 
THE JOURNAL OF EXPERIMENTAL ZOSlOGY, VOL. 9, NO. 4. 
