THE MEDUSAE. 



SCYPHOMEDUSAE. 



Students of the Scyphomedusae are so generally agreed that Haeckel's 

 ('80) classification of the group is in many ways unsatisfactory, that several 

 attempts have been made recently to work out a more natural grouping of 

 the various members of the class. These have been thoroughly reviewed by 

 Maas (: 07), so that I need not dwell here on the historic aspect of the sub- 

 ject. By far the most satisfactory classification which has yet been proposed 

 is the result of the successive studies of Glaus ('83), Vanhoffen ('92, : 02''), 

 and Maas (: 03, : 07). As provisionally outlined by the last author, (: 07, 

 p. 193), it is as follows: — 



A. Charybdeida. 



B. Three groups which together form a phylogenetic series. 



1. Stauromedusae, exclusive of the Tesserida. 



2. Coronata. 



3. Discophora. 



This scheme shows an important advance over the one proposed by 

 Vanhoffen ('92, p. 20), in abandoning the division of the Scyphomedusae into 

 Cathammata and Acathammata. Such a separation of the class into two 

 opposed groups, based on the presence or absence of septal nodes, is prob- 

 ably of no phylogenetic significance, since, as Glaus has shown, it is 

 doubtful whether the septal nodes of the Coronata and the long " Septal- 

 leisten " of Stauromedusae and Gharybdeida are homologous, it being 

 altogether likely that the septae, at least of the latter group, are not 

 homologues of the primitive taeniolae of the scyphistoma, but are new form- 

 ations on the part of the endoderm. Another serious objection to his 

 grouping is that it results in the close association, under the heading 

 Acoronata, of the widely divergent Charybdeida and Stauromedusae, an 

 association which Vanhoffen (: 02% : 06) has himself admitted to be irrational. 

 Lastly, employment of the presence or absence of septal nodes as the chief 

 criterion results in laying too strong emphasis on the distinction between 

 Coronata and Discophora. 



