174 J. W. Fewkes — Deep- Sea Medusae. 



Atolla, the same coronal fossa and coronal socles. It is most 

 closely allied to Nauphanta but has thirty-two socles instead of 

 sixteen, eight sense-bodies (?) and twenty-four tentacles.* These 

 tentacles are therefore arranged in threes, each series of three 

 alternating with eight sense-bodies. — All with gelatinous 

 socles. 



It is easy to interpret the three deep-sea Acraspeda,. Atolla, 

 Nauphanta, and Nauphantopsis. At first sight they closely 

 resemble gigantic young Aurelia or Cyanea in a stage which 

 is called the ephyra. This is especially true of Nauphanta, 

 which has the same number and arrangement of tentacles as 

 the young Cyanea or Aurelia in the ephyra stage. It is so 

 close, in fact, that at first sight they seem identical. In Nau- 

 phanta we have mature ovaries, and this would seem to indicate 

 the adult form. The existence, however, of ova, and a sexual 

 maturity is by no means an indication of the acquisition of the 

 adult form among medusae, and many instances might be men- 

 tioned of a jelly-fish with mature ova even before embryonic 

 appendages have been dropped. There is nothing then to 

 prove that Nauphanta is not the young of some other medusa, 

 and on the other hand there is no proof that it is not an adult. 

 If it is an adult, it is a mature medusa with likeness to embry- 

 onic conditions of other medusae. It would then be nearer 

 the ancestral form of Acraspeda than any of the more common 

 medusae like Cyanea and Aurelia. 



At first study, I was inclined to regard Atolla as a giant 

 ephyra of some unknown medusa. Its affinities are certainly 

 very close to Nauphanta and through the latter genus it is 

 connected with ephyra, the young of Cyanea. We may 

 therefore regard both these genera as embryonic in their struc- 

 ture and as close allies of the young of a higher jelly-fish. It 

 is a most interesting fact that two genera with such marked 

 characters are considered deep-sea genera. Exactly what the 

 evolutionist would expect from the uniformity of conditions 

 which exist in deep water, we find manifested in the simple 

 anatomy of two of the more characteristic deep-sea genera of 

 Acraspeda, a simplicity of structure of embryonic and there- 

 fore of ancestral nature. It is certainly strange that these 

 two facts are associated. It is an extraordinary coinci- 



* Nauphantopsis is an interesting genus in its relationship to the surface genus 

 Periphylla, which has four sense- bodies and twelve tentacles in four series of three 

 each. We likewise have in the same genus marked coronal socles, sixteen in 

 number, while Nauphantopsis has thirty-two. Nauphantopsis then appears to be 

 a connecting genus between Nauphanta and Periphylla. I believe we are justified 

 in regarding Nauphanta as an adult, although when I first studied it I was strongly 

 inclined to regard it an immature animal. It must be confessed that, with the ex- 

 ception that it has eight sense-bodies, while Periphylla has but four, there are 

 strong resemblances between a young Periphylla and the genus Nauphanta. 



