334 THE PRACTICAL FISHERMAN. 



One of these hearts has been lately very accurately described by Pro- 

 fessor E. H. Weber as occurring in a large species of serpent, the 

 Python vivitatus ; it is about nine lines in length and four in breadth ; it 

 has an external cellular coat and a thick muscular one ; four muscular 

 columns run across its cavity, which communicates with three lymphatic 

 vessels, all of which have valves ; the heart has also something like an 

 auricular appendage. Dr. Hall's discovery was made near the tail of 

 the eel, and was particularly observed under the microscope. If a 

 young eel, six or seven inches in length, be rolled up in a strip of linen 

 cloth, leaving out a portion only of the tail, it will remain quiet when 

 placed on a long slip of glass, and the pulsation may be readily discovered 

 to be wholly independent of the action or influence of the heart, and the 

 number of beats will be seen to be more than double in the same period of 

 time ; they also continue after the heart properly so called has been 

 removed. There can be no question that such an apparatus as this must 

 greatly promote the important process of absorption, and although it 

 may be supposed to be particularly desiderated in fishes and reptiles, 

 Professor Muller expresses his conviction that important discoveries 

 of a similar nature will ere long be made in the higher classes of 

 animals." 



It is characteristic also of the eel family that it has a peculiar kind of 

 bladder. This is of large size and long, and in the middle of it is what 

 may be termed a gland, covered with a network of bloodvessels, by the 

 action of which the air is probably secreted into the sac or air bag. 



On opening the eel from the throat the first thing that strikes the 

 operator is the strong and eminently vigorous heart-action, which, even if 

 txll outside movement has long since ceased, is frequently to be observed 

 performing its work some time after being exposed. Indeed, I have occa- 

 sionally carefully taken it out and placed it in a glass of water, where it 

 has continued its convulsive movement for twenty minutes or more, 

 according to the temperature of the water and time the owner of it may 

 have been out of the water before its extraction. It is situated just 

 below the final folds of the gill branchiae. 



Before referring to the generative organs of the eel I must not omit 

 to mention the parasites with which eels seem inveterately affected. On 

 opening a 31b. fish, November, '76, I perceived minute dark-coloured 

 threads, or rather worms, adhering to the mucous membrane of the upper 

 part of the ventral canal. These were in all stages of growth, from the 

 eighth of an inch (at which length they were transparent) to half an inch 

 in length, and about as thin as common sewing cotton. Whilst attached 

 to the membrane they were active, immediately on being detached they 

 died. I found them to be without a fully developed head, but with an 



