4 THE CRASPEDOTE MEDUSA OLINDIAS AND SOME OF ITS NATURAL ALLIES. 



The umbrella is moderately high, measuring nearly one-half as much as its largest 

 diameter, which is found slightly above the margin (PL I, Fig. 1); but in younger 

 examples (Fig. 2) it is relatively higher, as in many other veiled medusae. The jelly 

 is thick and very consistent. The manubrium is quadrate with distinct lips, and 

 when expanded hangs down into the umbrella cavity about two-thirds the height 

 of the latter. Of some forty specimens that I have examined for the purpose, only 

 three had four radial canals, and all the rest had six, so that there cannot be any 

 doubt that six is the normal number for the species. Two of the canals start from 

 two of the opposite corners of the manubrium, and of the remaining four two together 

 from the other opposite corners. A comparison of a few examples is, however, suffi- 

 cient to show that the number six is due to the bifurcation of two of the four 

 original radial canals. This is easily seen on the apical view of almost any example, 

 as shown in Figure 7, where two of the radial canals are seen to unite just before enter- 

 ing the central stomach, or as in Figure 8, where four of the radial canals forming 

 opposite couples are seen to have a common root for each couple. Examples with 

 two simple and two Y-shaped radial canals are not rare, and cases of five radia 

 canals are also met with, though seldom. 



The gonads are foldings of the subumbrellar walls of the radial canals, and extend 

 the greater part of their lengths, leaving only a small proximal portion and a much 

 smaller distal portion free (Fig. 6). In young examples these foldings are very simple 

 and are clearly continuous (PL II, Fig. 13), but in older ones they become more 

 complicated and are sometimes divided into numerous lobes, which are again subdivided 

 into secondary lobes (PI. I, Fig. 9). In the case of Y-shaped radial canals, the gonads 

 extend upwards only as far as the point of division, and are therefore V-shaped. If 

 the point of division lies very near the manubrium, however, the gonads leave a small 

 proximal portion free, as in the normal case. 



The endoderm of the radial canals presents different aspects on the oral and 

 aboral sides. On the latter the cells approach nearly to the cubical form, and the 

 cytoplasm is usually deeply stained and contains a comparatively small number of 

 minute granules, while on the former the cells are tall and contain numerous large 

 granules, which are probably a product of assimilation and form a reserve material. 

 It must be remarked in this connection that the amount of these granules varies a 

 good deal according to the nutritive condition of the example, and that in a specimen 

 which in some way or other had lost its manubrium these granules were almost wholly 

 absent. The endodermal lining of the gonads is composed entirely of these cells con- 

 taining large granules. 



The circular canal is very large, and the endoderm presents the same difference of 



