12 



sends the blood into the ventricle, the two cavities being 

 apparently separated by a muscular substance. The 

 auricle and ventricle are crimson red, and are conspicuous 

 objects. Towards the upper portion of the auricle a valve 

 exists, but I could not clearly ascertain this by examination. 

 The ventricle has a bulbous thickening towards the junction 

 ■with the artery which supplies the branchise ; the blood 

 here traverses the leaflets of the gills, and from thence it 

 is collected into an aorta, a great dorsal artery, which dis- 

 tributes it to all parts of the animal. It is wonderful and 

 instructive to see this circulation. The blood disks, where 

 they pass through the smaller vessels of the capilaries, are 

 squeezed into an oblong shape, the return of the blood can 

 be traced into the veins, in which, from their larger size, 

 they resume their proper figure. There is a peculiarity in 

 the circulation in the tail of the fish, which has been before 

 observed and I think mentioned by Mr. Buckland, but I 

 have not been able to read what has been written on this 

 subject, and give you but the results of my own observa- 

 tions, which are as follows: — When the young salmon is 

 only a few days old, on examining its tail, it will be found, 

 in the first place, that the dorsal vertebra bend at right 

 angles and form a caudal extremity similar to that shown 

 in the cartilaginous fishes, the Sturgeon and the Shark 

 and Kay. At this time no appearance of rib is seen in 

 the caudal fin, but it is abundantly supplied with blood 

 vessels, which ramify in a radiate form firom the end of the 

 dorsal arteiy, where this caudal vertebra bends, and the re- 

 turn blood brought back by the veins, which all converge 

 towards this point, collects in a sort of sinus, from whence 

 it appears propelled into the dorsal vein towards the heart. 

 I say appears, for it is difficult to determine if the accelera- 

 tion of the blood is due to a determined action of this vessel 

 or from its escape into the much larger calibre of the dorsal 

 vein. I believe this vessel (whatever may be its nature) 

 has given rise to the statement that the young salmon has a 

 heart in his tail. The drawing I here exhibit shows what 

 I describe. 1 have drawn the heart of the tail as if it 

 had a valve, having on one occasion thought I detected it. 



