242 HARGITT. [OL. II. 



seen in comparing these ratios with those concerning the radial 

 canals, there is here again a slight tendency toward the smaller 

 or trimerous forms, though not specially marked, especially 

 when account is taken of the fact that only on specimens with 

 more than the normal canals would additional gonads be 

 found, while it was not rare to find in tetramerous forms speci- 

 mens with only three gonads, or even less, one tetramerous 

 specimen having a single gonad. Concerning variations of the 

 several gonads of individual specimens no account was taken, 

 owing to the difficulty of determining relative differences in 

 organs loosely suspended in sinuous folds, as are these in Goni- 

 onemus, and by the further fact of the continued growth and 

 successive discharge of the sexual products, as seems to be the 

 case here. 



Manubriitni. 



As in most medusae, the manubrium is a rather prominent 

 and important organ. In correlation with the tetramerous 

 organization of the medusa, the manubrium, including in this 

 general term the basal gastric pouch and oral opening and lobes, 

 is of similar form and adjustment. As will be noted, how- 

 ever, by a comparison of the several tables, there are many 

 exceptions, or, in other words, considerable variation. In most 

 cases, however, as comparison will show, there is in the varia- 

 tion an obvious correlation with other variations, notably with 

 that involving the radial canals. But here again the exceptions 

 are sufficiently numerous to warrant the conclusion that there 

 is in this organ itself individual variation, apparently devoid of 

 any adaptive end or relation. 



Aside from the facts of meristic nature above noted, there 

 are features of variation which would seem to be of a purely 

 substantive character. For example, in several specimens the 

 manubrium was greatly extended lengthwise, reaching in some 

 cases quite beyond the velum, occasionally as much as one- 

 fourth its total length. While of course this organ is very 

 extensile, yet in many hundreds of specimens examined alive, 

 in many cases while the animal was engaged in engulfing food, 

 I have never seen the manubrium extended beyond the velum. 



