216 Miscellaneous. 



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

 fonnd the anul fin, so well concealed that some ven- 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 float the ova or the hatched }oung. 



The development of the Lopliobranchs offers some interesting and 

 rather impoi'tant facts. Thus ^l. Canestrini has observed that the 

 IlippDcmnpi have, during the initial ])ortion of theii' 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 Ntrophls Jnmhrkifonnis 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 Hippocam^ii. These fishes are 

 distinguished, when adult, from the Sip7io)iostomi and Si/nr/nathi by 

 the absence of a caudal fin. But on examining indiriduals of I/ij)- 

 pocamjius brevirostris of 5| millims. length, M. Canestrini discovered 

 that tlaey possess a caudal tin perfectly distinct, though little deve- 

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

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

 without a trace of raj's. This observation becomes very important 

 when we remember that in the eocene period there were Hii)poaimpi 

 with a caudal fin — a character considered by Agassiz sufficient 

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

 the name of Calamostoma. C. hrevkuhnn, Ag., bears a very distinct 

 rounded fin. 



M. Canestrini relics on these embrj'ological and pala^ontological 

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

 arrives at this conclusion — that Neroj>liis is descended from Sijn- 

 cpiathxs, and JJij^jiocanqnis from Cahiniostoma. He says : — 



" The S)/ngtiathi, in losing the pectoral fins and the caudiil, have 

 given birth to the JVerojihcs, 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 SipufnatJiKS, or the genus Nc- 

 rojihis?' 



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

 the S)/)u/))at?ii (furnished with a Avell- developed caudal) and tlie 

 NeropJu's ((juite destitute of a caudal) there exist other A(/-o/'/(r>". 

 Avhich possess when adult a rudimentary caudal, and ccnistitute 

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

 of this assertion I may mention Neroj^Jiis tou/niueci, N. Heckeli, and 

 N. mjHorca, all of which have a rudimentary caudal. 



"One may with peifeet safety say W\ix{ Nerophix is a genus in 

 process of formation. Wlien the caudal fin. aheady at the mast 

 rudimentary, shall lie rntncly atrophied in all the species, and shall 



