Variations Among Scyphomedusce. 563 



Variations in the Adults. 



As in the study of the ephyrae attention was directed chiefly to 

 the marginal or sensory bodies, and to the central or vegetative, 

 so likewise in the study of the adults the same systems have received 

 primary consideration, though in the latter including also the 

 canal system, as a correlating medium between the others. 

 Attention was also directed to the problem of the probable influence 

 of local conditions in determining variations. As favorable 

 localities from which to secure specimens more or less subject to a 

 definite environment, New Bedford harbor andWaquoit Bay were 

 selected, the latter serving moreover, the further end of ascertain- 

 ing the variations exhibited by ephyrae and adults under the same 

 environment. 



In addition to authorities cited in a previous part of this paper 

 attention may be directed to the observations of Bateson and 

 Romanes on the variations of Aurelia aurita. The latter has 

 described in some detail variations found in this medusa and has 

 illustrated by diagrams many of the features described. In both 

 the illustrations and the analysis of the facts there is an apparent 

 eff^ort of the author to reduce the variations to as few symmetrical 

 types as possible. As I have pointed out in another connection 

 in reference to the work of Ehrenberg and Agassiz, these attempts 

 to discover a law of symmetry, or perhaps better in modern 

 phrase, a law of regulation, in the diverse variations encountered, 

 have apparently been only partially justified. While it is doubt- 

 less true that in many cases, perhaps in a majority, some form of 

 regulation may be distinguished, there are too many cases in 

 which this is lacking to be considered as merely exceptions to 

 such a law. A study of the following facts and illustrations, will 

 I beheve justify this view. 



As Bateson in commenting upon Romanes' work has remarked, 

 "It is impossible in regular threes, sixes, etc., to say that any 

 particular segment is missing or added rather than another." 

 And if this be the case with an organism like Aurelia, in which 

 the several organs are so sharply differentiated as to be easily 

 distinguished at a glance, it is much more likely to be true in 

 organisms of more complex structure and less sharpness of 

 difl^erentiation. 



In an attempt to ascertain the comparative frequency of certain 



