784 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. [38] 



from the cartilage of the primoidal cranium, with which it is in no way 

 connected, by its much denser cartilage cells. 



In many cases among the Selachii, too, does the nasal alar cartilage 

 encircle these apertures as a ring, sending out processes into the nasal 

 valves. If one pictures to himself that the nasal valves of the Sela- 

 chians have become merged with each other during their growth or de- 

 velopment, and the cartilaginous processes contained within them be- 

 come blended, there will result as a consequence a condition that can 

 in no way be distinguished from the state of things as seen in the Tele- 

 ostei. That this view is the correct one is shown by the history of 

 the development of the nasal organ in the bony fishes. 



In newly-born fishes there exists on either side a simple undivided 

 nasal aperture, as I have observed in the Lota vulgaris^ in the Pike, in 

 the Trout, and in the Chondostroma nasus. It is not until these forms 

 have passed the embryonic stage does there occur, sooner or later, 

 a division of this aperture into anterior and posterior nares. Both 

 the median and lateral periphery develops a small patch of skin, 

 directed towards the center of the aperture. Very soon these processes 

 that correspond to the nasal valves in the Selachii become contiguous, 

 the lateral process being behind the median in all of the specimens ex- 

 amined by me. At this stage the nares in osseous fishes have reached 

 the precise condition that remains permanently in ]!^otidanides and 

 Aeanthias. 



In a short time these two nasal valves of bony fishes blend together 

 and the narial opening receives its definite shape, at least for those 

 forms in which the two apertures are situated close to each other. In- 

 asmuch as the primary conditions are not exactly so arranged in Lota 

 vulgaris, whose anterior and posterior nares, after it has arrived at 

 maturity, are far removed from each other, there must occur in this 

 species a widening of the nasal bridge and a separation of the nasal 

 apertures at a later period (unfortunately I lack the material to illus- 

 trate these stages). At any rate fishes with the anterior and posterior 

 nares close together are to be considered as primitive forms, and from 

 such, forms can be traced in which these apertures are far apart. Such 

 forms, then, are to be considered as the highest in the scale of develop- 

 ment in a certain direction, in which the narial apertures are far apart 

 and are situated on the upper lip. 



Such formations among bony fishes occur in Ophisurus and kindred 

 forms,"*® in the family of Muraenoids, and, in fact, they have at the first 

 glance a certain resemblance to corresponding structures in Dipnoi and 

 perennibranchiates, and it does not appear improbable to me that this 

 peculiarity of the Ophisurus led Balfour to* assert a homology of the 



••^Liitken, Nogle BemaerJcninger om Naeaeboreunea Stilling hoa de i Gruppe med Ophiau- 

 ru8 staaende Slaegter af Aale familien. VidensJcahl. Meddeleher fra d. nuturhistorislce 

 Forening i Kjobenha/on, 1851. 



