Fewkes.] 394 [Nov. 2, 



suit of its peculiar mode of life ? I believe it is. I believe that the 

 modification in the hydroid Hydrichthys, the loss of tentacles, the 

 polymorphism, and the increase in prominence of the sexual 

 bodies, are exactly what we should expect to find a priori if a deg- 

 radation had taken place in its structure. 



There is one other point to which I wish to call the attention of 

 the Society before closing my communication. The existence of a 

 polymorphism, such as we find in Hydrichthys, is exceptional 

 among fixed hydroids of the tubularian group. Something similar 

 exists in Hydractinia and Perigonimus and one or two other genera, 

 but this kind of polymorphism is not common among fixed Hydro- 

 medusae. A similar polymorphism exists, however, in Velella, a 

 floating hydroid well known to all naturalists. In Velella we 

 have the basal plate with anastomosing tubes of Hydrichthys mod- 

 ified into a complicated float. The gonosomes are the same in both 

 genera, the filiform bodies of Hydrichthys are represented by the 

 single central polyp, so-called, in Velella. The medusae of the 

 two closely resemble each other. There are only two kinds of in- 

 dividuals in both genera. 



Strangely enough, after I had reasoned out this likeness between 

 Velella and Hydrichthys, on morphological grounds, my memory 

 went back to a strange story I had once heard from an Italian 

 fisherman of the origin of Velella from the common mackerel. 

 This story or a similar one long ago found its way into the books. 



According to Marcel de Serres, the Mediterranean fishermen sup- 

 pose that Velella originates as a bud from the head of the mackerel, 

 and Pagenstecker goes on to explain this error, after quoting its 

 source, from the fact that young Velellae are often found in the nets 

 with the fishes, and it is easy to suppose, as their color is similar, 

 that one budded from the other. While we accept without ques- 

 tion this explanation and the want of foundation of the fisher- 

 men's yarns, it is a strange coincidence that a possible relative of 

 Velella should be found attached to the body of a fish. It is well 

 for us to enquire, in the light of phylogeny, whether Velella, if it 

 has not itself originated from hydroids on the fish b}' budding, has 

 not been directly derived from one which is so intimately related 

 to Hydrichthys, which is attached to the body of a fish, that an 

 unskilled observer might be easily deceived. 



Hydrichthys is, in point of fact, the nearest known ally of Velella 

 among fixed hydroids, and their morphological likenesses have 



