216 Miscellaneous. 



the swollen walls of the anterior part of the sac. In this duct is 

 found the anal fin, so well concealed that some very accurate ob- 

 servers, such as Van der Hoeven, have denied its existence. The 

 movement of this fin must facilitate the renewal of the water in 

 which fioat the ova or the hatched young. 



The development of the Lophobranchs ofi'ers some interesting and 

 rather important facts. Thus M. Canestriui has observed that the 

 Hippocampi have, during the initial portion of their life, a snout of 

 normal dimensions ; so that the characters of the order only appear 

 in them at a rather advanced period of their development. 



Dr. Fries remarked that Nerophis lumbriciformis in the young state 

 possesses very distinct pectorals and an embryonic fin comprising 

 the caudal, while in the adult state it is entirely destitute of the 

 former and has only a trace of the second under the form of a dorsal 

 fin. A similar thing occurs with the Hippocampi. These fishes are 

 distinguished, when adult, from the Siphonostoml and Syngnathi by 

 the absence of a caudal fin. But on examining individuals of Hip- 

 pocampus brevirostris of 5| miUims. length, M. Canestrini discovered 

 that they possess a caudal fin perfectly distinct, though little deve- 

 loped. It is formed by a prolongation of the skin which covers the 

 posterior extremity of the animal, and consists of membrane only, 

 without a trace of rays. This observation becomes very important 

 when we remember that in the eocene period there were Hippocampi 

 with a caudal fin — a character considered by Agassiz sufiicient 

 to separate them genericaUy from those of our present seas, under 

 the name of Calamostoma. G. breviculum, Ag., bears a very distinct 

 rounded fin. 



M. Canestrini relies on these embryological and palaeontological 

 facts in order to establish the genealogy of the living genera. He 

 arrives at this conclusion — that Neropliis is descended from Syn- 

 gruitlms, and Hippocampus from Calamostoma. He says : — 



" The Syngnathi, in losing the pectoral fins and the caudal, have 

 given birth to the Nerophes, which still preserve during the em- 

 bryonic period, and as a proof of their origin, those same fins 

 which their ancestors retained during their whole life. 



" These conclusions may seem to some persons too premature ; 

 and they will ask, as do all the opponents of these ideas, ' Where 

 are the links which ought to unite the two?' or else, 'Which 

 is the derived form ? the genus Syngnatlms, or the genus Ne- 

 rophis ? ' 



" I am, fortunately, able to answer this question, because between 

 the Syngnathi (furnished with a well- developed caudal) and the 

 Nerophes (quite destitute of a caudal) there exist other Nerophes, 

 which possess when adult a rudimentary caudal, and constitute 

 as it were a transition between the extreme forms. In support 

 of this assertion I may mention Nerophis angidnea, N HecJceli, and 

 N. cequorea, aU of which have a rudimentary caudal. 



" One may with perfect safety say that Nerophis is a genus in 

 process of formation. When the caudal fin, already at the most 

 rudimentary, shall be entirely atrophied in all the species, and shall 



