BDELLOSTOMA DOMBEYI, LAC. 157 



allowed for. The desired vertebrate was found in Bdellostoma, 

 which thus presented me with material for both morphological 

 and physiological investigations. Physiological operations on 

 the ear of Cyclostomes have been tried on Petromyzon only, so 

 far as I know, and then they were abandoned without obtain- 

 ing results, on account of the difficulty of the operations. The 

 first operations I performed were on anaesthetized animals ; but 

 I soon abandoned the use of anaesthetics for several very 

 sufficient reasons. 



My method of operation was the following : In order to 

 hold the extremely slimy and slippery animal, I used large 

 sheets of blotting-paper, such as botanists require for drying 

 plants. Bdellostoma was taken from the aquarium, and at 

 once rolled up in the sheet in such a fashion as to hold it 

 extended during the operation. One sheet makes a roll suffi- 

 ciently stiff to retain the fish perfectly. A stout needle was 

 thrust through the skin at the side of the mouth, and another 

 through the skin and muscles of the tail, and both forced into 

 the table at such a distance apart as to prevent the fish from 

 squirming or crawling out of the paper cylinder. The blotting- 

 paper was removed over the region of the ear, and an incision 

 made through skin and muscle, exposing the cartilaginous 

 ear capsule. The top of this was shaved off with a sharp 

 scalpel of suitable shape and size, and the auditory nerves 

 cut inside the ear capsule, either with a scalpel or scissors. 

 The columella was then cut, and the ear lifted out with 

 forceps or with a small bent needle. An examination was 

 made with a lens to see if any part of the ear or auditory 

 nerve had been left in the capsule, and any such fragments 

 were removed before the cut in the skin was sewed up. This 

 done the animal was unrolled into the aquarium, and its 

 motions watched. The whole operation does not require more 

 than two minutes, and the fish does not appear to suffer in the 

 least from suspended respiration, so far as I could make out. 



A fish thus operated upon, with both cars removed, will 

 swim from the moment it is placed in the aquarium like a 

 normal fish. In some cases the creature will tie itself into 

 a knot, with the evident purpose of removing the irritation 



