156 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



ON CERTAIN FEATURES OF THE DEVELOPMENT OF THE SALMON. 



By JOHJV A. RlfDEB. 



So imich lias been written upon the anatomy and development of this 

 fish by eminent authorities that I approach the subject with a cer- 

 tain hesitancy. The development of the skull has been elaborately 

 worked out by W. Kitchen Parker. The skeleton of the adult has been 

 figured in great detail by Bruch in a magnificent monograph, while 

 the general development has been repeatedly discussed by investi- 

 gators during the last century with more or less thoroughness. Not- 

 withstanding this, it may be truly said that our knowledge of the exact 

 details of some features of its development is still imperfect, even 

 though such able euibryologists as OEllacher, Balfour, His, Hoffmann, 

 and Ziegler have devoted considerable attention to it and its allies 

 within a i^eriod extending over scarcely more than the past decade. 



The early stages of development have been investigated by OEllacher, 

 His, and Ziegler, with such opportunities that can only be enjoyed by 

 one who is near a locality where the spawning or oviposition of the 

 adults is in progress. I can therefore add nothing to the information 

 given us by those writers, but all that will concern us at present is the 

 arrangement of the blood-vascular system at the time of hatching, 

 some of the impairments which this system suffers when the youug 

 fishes are under the care of the fish-culturist, and the development of 

 the fins. 



The material used in this investigation consisted of recently-hatched 

 embryos of the land-locked salmon, Salmosalar, var. sebago. I have 

 carefully drawn a live specimen several times enlarged by the help of 

 the camera lucida, as represented in Fig. 1, in order especially to show 

 the arrangement of the vessels on the vitellus, the distribution of the 

 rose-colored oil drops in the latter, and the vessels and venous sinus 

 in the tail. 



The mode of development and outgrowth of the fins is especially in- 

 teresting, the more so since Professor Cope has recently reached the 

 conclusion that many of the so-called "Ganoids" of the Palaeozoic 

 rocks seem really to be affiliated to a great and important order of ex- 

 isting fishes embraced by that author under the term IsdspondijU, which 

 includes the existing Salmonoids, Clupeoids, Hyodonts, Albulids, «&c. 

 As it therefore seems that the salmon belongs to a very ancient series 

 of forms dating back phyletically to the Devonian, it may be well for 

 us to examine into the development of the fins to see if that process 

 would really give countenance to Professor Cope's views. 



I. The vertical fins.— This set of fins is developed from a median fold 

 extending from a vertical slightly behind the pectorals back over the 

 end of the tail, thence forward on the ventral side to the posterior side 



