AEGINIDAE. 71 



Maas (: 04 a , : 04°) believes that the adradial pockets of the Aeginidae 

 are derived by a process of subdivision from radial pockets. But the occur- 

 rence in the present collection of a young specimen of Aegina with interradial 

 pockets equal in number to the tentacles suggests that Haeckel (79) may 

 after all have been correct in maintaining that an interradial location of the 

 gastric pouches is the primitive one in this family. 



Recognition of the fact that the presence or absence of a canal system is 

 not of so much systematic importance as Haeckel supposed, and that the con- 

 dition of the gastric pockets, whether simple or divided, is very significant, 

 has lead Maas to remove from the Cunanthidae those genera with bifid 

 pockets which Haeckel has included in that family on account of the (sup- 

 posed ?) presence of peripheral canals ; and to transfer them to the Aeginidae. 

 When this is done it appears that at least two of them are identical with 

 genera which Haeckel himself has classed under the latter family. 



Taking the number of radial parts as the chief generic character, the 

 following well-defined genera may be distinguished: — 



1. Four tentacles; eight or sixteen gastric pockets 



in adult Aegina (Cunarcha) . 



2. Eight tentacles ; sixteen or thirty-two gastric 



pockets Aeginura (Cunoctona, Aeginodiscus). 



3. Two tentacles ; four peroniae ; eight gastric 



pockets Solmundella (Aeginella). 



4. Four tentacles ; eight peroniae ; sixteen gastric 



pockets Aeginopsis. 



Solmundella and Aeginopsis are made by Vanhoffen (: 07) the basis of a 

 separate family, Aeginopsidae ; but their affinities with the other Aeginidae, 

 in conformation of the gastric pockets and lack of otoporpae, are very close. 

 I have already (pp. 48, 49) discussed Vanhoffen's disposition of the other 

 genera here grouped in this family. 



The problematic species Citnissa polypora Haeckel, with sixteen tentacles 

 and thirty-two gastric pockets, would form the basis of still another genus 

 should it ever be demonstrated that there is any such Medusa. And it is 

 probable that the extraordinary genus Hydroctena of Dawydoff (: 04), if it 

 proves to be anything but a larval Solmundella, as is suggested by its 

 resemblance to the stages in the development of that genus described by 

 Woltereck (:05), must find a resting place in this family. 



It seems to me that the following genera and species, included provision- 

 ally by Maas (: 04°) among the Aeginidae, may as well he removed from this 



