No. 5-] VARIATION AMOXG IIYDKOMEDUSA //. 



237 



tendency is shown in PI. Ill, Fig-. 6, where only the vestige of 

 the fourth canal is shown, the reduction in extent of two 

 others, with the further correlation of the evidently bilobed 

 condition of the gastric pouch. 



(2) Asymmetry. This is more or less consequent upon the 

 atrophy already noted, as will be seen from a comparison of the 

 figures just cited, and involves to a certain degree the entire 

 organism, gastric and oral symmetry, no less than that of the 



FIG. ii. Tetramerous specimen of very unsyfnmetrical type. 



bell and tentacles. Some further reflections on these lines will 

 more naturally come up in connection with later discussions. 



Another type of variation is shown in PI. Ill, Figs. 1-5. In 

 these specimens, while the tetramerous type is more or less 

 evident from the number of canals, gonads, or gastric pouches, 

 still there is a rather definite tendency toward a trimerous 

 aspect of the medusa as a whole, so far as the segmentation of 

 the body is concerned. In Fig. I, while there is a clearly 

 tetramerous condition exhibited which extends to the several 

 organs involved, there is yet such an approximation of those 



