44 



A HISTORY OF FISHES 



those in which the apertures are reduced. This is due to the 

 fact that as the filaments dry up they tend to stick together and 

 are thus mechanically prevented from functioning. The im- 

 portance of moisture in enabling a fish to cling to life is em- 

 phasised by the length of time some fishes will remain alive if 

 packed in damp grass or other vegetation. The author has 

 more than once received a parcel containing Roach or Bream 



Fig. 19. EXTERNAL GILLS. 



A.I. Young South American Lung-fish (LepidGsircn paradoxa), 30 days after 

 hatching, X 3 ; A.2. The same 40 days after hatching, X 2 ; B. Young Bichir 

 {Polypterus endlicheri), X i^. 



thus packed, which have come to life successfully several hours 

 after capture when tipped into a bowl of water. Fresh-water 

 Eels (Anguilla) are able to survive for a considerable time away 

 from their native element, and to wriggle across damp grassy 

 meadows at night in order to get from one piece of water to 

 another. It had always been supposed that these land excursions 

 were made possible by the small size of the external gill- 

 openings, but a French investigator has shown that Eels from 

 which the gill-covers have been cut off were able to live out 



i 



