75 



A curious discovery of pulsation in the tail of the eel was made by Dr. 

 Marshall Hall, in 1831. This pulsation is wholly unconnected with the heart, and 

 beats more than double in the same time. Dr. Muller, Professor of Physiology at 

 Bonn, found that these pulsating sacs in the batrachia— such as the frog, sala- 

 mander, and others — contain lymph, and direct its motion. The pulsation in the 

 eel is probably lymphatic. 



The electric eel (Gymnotus eleetricus), not being one of our fishes, I merely 

 allude to it, for the sake of noticing the singular fact that, so long ago as the days 

 of Anthony and Cleopatra, their physician, Dioscorides, recommended, for medical 

 purposes, the shock of the electric eel — the earliest record extant of the application 

 of electricity to medicine. 



The last fish to which I shall now refer is the lowest in this division of the 

 animal kingdom— the lamprey (petromyzon). We have four species in England ; 

 three of which, if not the fourth, are found in the rivers of this county. Two of 

 them (P. fiuviabilis and P. plauerii) are often called lamperns ; why, it were per- 

 haps difficult to say, unless to puzzle Ichthyologists. They are true lampreys. 

 By means of their circular fleshy lips they adhere firmly to stones or fish ; piercing 

 the strongest integuments of the latter and preying on their substance. 



To those who have never examined this remarkable fish, it must seem utterly 

 incomprehensible, how, when adhering closely to any object by means of the 

 mouth, the process of respiration can be carried on. But like everything else in 

 nature, it is modified in accordance to the circumstances in which it is placed. 

 Most fish have free gills, which open to expel the water that Lsis been taken in by 

 the mouth. But the lamprey is constantly so situated as to make this process 

 impossible ; it is, therefore, supplied with a power of breathing by means of external 

 orifices, through which the water is both inhaled and ejected — altogether 

 independent of the mouth. 



The marine lamprey is found in the Wye, as well as in the Severn, during 

 summer. Like all sea fish that mount the rivers, its purpose is to spawn. This it 

 does in pairs, while the smaller species congregate in large masses. 



The common river lamprey was supposed to visit the sea. Mr. Yarrell says 

 that his own observations lead to a contrary conclusion. I have myself seen it in 

 the Wye early in February —long before the marine lamprey has left the salt 

 water ; and hence conceive that Mr. Yarrell is right. The pride is much smaller 

 than the others ; and though often called the mud lamprey, it is not a real lam- 

 prey ; for as the mouth does not form a circle, it is incapable of adhering to stones 

 or any other object. 



Between those fish that swim near the surface— such as the trout, and those 

 that live at the bottom, as the flounder, loach, and eel — there is a great and im- 

 portant distinction. The former have a higher standard of respiration, a lower 

 degree of muscular irritability, a greater necessity, for oxygen, die almost, as soon 

 as taken out of the water, and whose flesh quickly decomposes. While such as 



