CASSIOPEA XAMACHANA. 199 



the whole extent of the mouth parts. Among them the central, radial, and primary 

 vesicles were hardly distinguishable, although so easily recognized by their greater size 

 in the typical form of the species. 



Another peculiarity was a projection of the mesogloea on the oral side of each 

 subgenital osteum, so that the interradial diameter of the oral disc was considerably longer 

 than the radial diameter, as shown in the table. These specimens presented also some 

 peculiarities of coloring, which will be noted in the next section. 



Color. The coloring of this semi-transparent animal consists of certain white mark- 

 ings, together with shadings of subdued tints of brown, green and blue, that are often 

 very beautiful. 



If we turn the aboral side (Fig. 35) of the medusa toward us we find often a brown- 

 ish band encircling the disc at the periphery of the concavity and shading off gradually 

 on both sides. Deeper within the mesogloea there is a much wider white circular band 

 extending under the brownish one ; and white bands, or spots, extend in a radial direction 

 outward from this along the marginal ridges. There is one spot to each ridge, and it 

 reaches nearly to the tip of the marginal lobe. The bands on the rhopalial lobes are inter- 

 rupted, however, by a roughly circular, transparent area over each rhopalium ; and in 

 many specimens, especially young ones, the interrhopalial (velar) spots are not fused with 

 the circle. On the inner side of the circular band of white there is a circle of large white 

 spots, "rhopalial spots," or stripes, that lie deep in the substance of the exumbrella and 

 are visible through the mesogloea, one in the radius of each rhopalium. The spot is 

 elliptical in outline, and extends from the white band to a point about two fifths of the 

 distance between the periphery of the concavity and the edge of the stomach. These 

 spots, while usually continuous with the band, like the marginal spots, are not always so. 



At the centre of the umbrella the stomach and subgenital cavities may be seen 

 through the mesogloea as a reddish brown circular area with a diameter of about one 

 fourth of the total diameter of the disc ; while surrounding the stomach there is a deep 

 blue halo with points that extend outward between the last-mentioned bands of white. 



Now if the animal be allowed to return to its usual position, the subumbrellar surface 

 will be found to be pretty evenly stippled by the greenish brown cells in the mesogloea. 

 Apparently beneath this stippling there is a blue pigment forming a circle around the 

 margin of the stomach and extending outward in broad bands, one along each interrho- 

 palial radius, nearly or quite to a large, more or less distinct patch of blue, that lies close 

 to the margin between every two rhopalia. The radial canals, and the fine, connecting 

 network of tubes, appear as rather indistinct, opaque, white lines. 



The mesogloea of the oral arms is transparent and colorless, except for an opaque 

 white stripe beneath the dorsal surface of each arm., of the same character as the white 



