6o4 



SCIENTIFIC NEWS. 



[Dec. 14, 1888. 



proceed to wander over the neighbouring country, and 

 appearing, as they do, immediately after the rain has 

 ceased, give rise to the impression that they have 

 actually been brought down by it from the clouds. 



Although they can thus live interred, as it were, for a 

 considerable time, it would seem that the presence of 

 some slight degree of moisture is indispensable to their 

 welfare, for it has been found that, if a cloth be laid 

 over the mud beneath which they are lying, they shortly 

 become stupefied and die. That, of course, is because 

 the air-supply is cut off. But they cannot breathe air as 

 we breathe it, for the simple reason that they possess, 

 not lungs, but gills ; and therefore oxygen, to benefit 

 them at all, must be obtainable through the medium of 

 water. Now the fish, seeming to be instinctively aware 

 of this fact, is careful to bury itself at such a depth in 

 the mud that the moisture cannot wholly disappear, no 

 matter how thoroughly the surface may be baked and 

 hardened. And by this moisture air is absorbed, and 

 from it transferred to the gills. Even from a depth of 

 more than two feet are these fish sometimes disinterred. 



Eels again are great travellers, and will cross large 

 meadows in search of more congenial quarters. But 

 they prefer to do so by night, when the herbage is moist 

 with dew, and seldom or never pass over a perfectly dry 

 surface. And there are numbers of other fish which 

 systematically leave the water in search of food, although 

 not for periods so prolonged. Thus the Jumper Fish 

 (Salarias tridactylus), resident in the seas of the Indian 

 Archipelago,constantly springs out of the water, scrambles 

 about over the stones and rocks lying upon the beach, 

 and snaps up flies and various other small creatures in 

 multitudes. And it can even climb up an almost per- 

 pendicular surface, adhering so tightly to its hold that the 

 waves beat upon it in vain. The Shanny (Blennius 

 pholis), when the tide is retreating, commonly takes up 

 temporary quarters in some convenient crevice, and there 

 remains for some four or five hours until the water 

 returns. And Mr. Couch tells us that he has known a 

 specimen to be perfectly vigorous and lively after no less 

 than thirty hours' confinement in a dry box. And there 

 is an extraordinary little fish known as Anableps tetroph- 

 thalmus, or Four Eyes (so termed by reason of the 

 apparent division of each eye into two parts), which 

 behaves very much like the Jumper, and seems quite 

 indifferent as to whether it is in the water or not. 



Now the power of all these fishes to remain out of 

 water obviously depends entirely upon the structure of 

 the gills. A fish breathes by taking in water through 

 the mouth, and expelling it through the apertures situated 

 upon either side of the neck, a portion of the oxygen 

 being abstracted by the gills during its passage ; not, of 

 course, the oxygen entering into its actual composition, 

 but that which is dissolved in it by absorption from the 

 atmosphere. And when a fish is brought to land it dies, 

 not because the air is actually injurious to it, but because 

 the delicate gill-membranes become dry and collapse 

 against one another, thus stopping the circulation. There- 

 fore it follows that those fish whose gills retain their 

 moisture the longest will best endure removal from the 

 water. And in such species as those described above, a 

 special structure is provided by which a certain amount 

 of moisture is retained and stored up, and in such a 

 manner that the gills can be moistened as often as 

 required. In the Climbing Perch, for example, the 

 pharyngeal bones which support the orifice between the 

 mouth and the gullet are not only greatly enlarged, but 



are modified in such a manner as to form a most elaborate 

 series of cells wherein water can be stored away very 

 much as it is in the cells of a camel's stomach. And a 

 little of this water passes to the gills whenever necessary. 

 In the Ophiocephali a tolerably large cavity lies just above 

 the gills with which it possesses direct communication ; 

 and within this cavity a considerable amount of water 

 can be retained, and doled out from time to time in such 

 small quantities as may be necessary. And there is a 

 somewhat similar arrangement in the case of the eels. 

 Thus in all these fish existence can be maintained upon 

 land until the moisture in the reservoirs is exhausted ; 

 and that moisture, as fast as it passes to the gills, absorbs 

 the oxygen from the air, to give it up immediately after- 

 wards to the minute vessels with which the respiratory 

 organs are closely studded. And so a structure is pro- 

 vided upon which the existence of the vast majority of 

 individuals absolutely depends. Living under such con- 

 ditions as those in which they are placed ; liable, and 

 indeed almost certain, during the months of summer, to 

 be stranded by the subsidence of their native 'streams : 

 nothing but the power of migration could save them from 

 destruction. Therefore are they enabled for a time 

 almost to set at nought the very laws of their being, and 

 by a slight modification of structure to breathe through 

 water even while living in air. 



Herons and Heronries. — Mr. E. A. Fitch, F.E.S., 

 communicates an interesting paper on this subject to 

 the Essex Naturalist. The principal heronries still exist- 

 ing in Essex are those of Boreham, Birch, Wanstead, and 

 St. Osyth. A heronry, however romantic it may seem, 

 is an almost unbearable nuisance, both on account of the 

 noise and the stench. Herons prey not only on fish, 

 but on mice, rats, rabbits, snipe, young ducks, etc. 



Colias Edusa at Woodford. — A male specimen oi 

 this species has been caught, according to the Essex 

 Naturalist, at Woodford, in that county, as late as Sep- 

 tember 7th. In 1877 this butterfly, known as the 

 " clouded yellow," occurred in thousands in Essex, as well 

 as in the other eastern and southern counties. Since 

 then, according to Mr. W. Cole, it has been very rare, 

 though its food plants are abundant in every parish, and 

 we have had seasons, to all appearance, as suitable as 

 that of 1877. 



A Parasite Destructive ro Sardines. — M. L. 

 Joubin has read before the Paris Academy of Sciences 

 an account of a parasitic crustacean, which occasions 

 serious havoc among the sardines on the western coasts 

 of France. The presence of this pest was first noticed 

 by M. Moreau, in the spring of 18S7. M. Joubin finds 

 that it belongs to a genus nearly allied to the Lerneonoma 

 or Lerneascus. It consists of a rounded head from two to 

 three millimetres in diameter, armed with three large 

 recurved horns, and antennae of the shape of nippers. 

 It iias a long neck, a cylindrical thorax, and a short abdo- 

 men, followed by large ovaries. The head and a part of 

 the neck are buried in the body of the fish, and the re- 

 curved horns prevent its extraction. The parts of the 

 sardine which it chiefly attacks are the hinder end of the 

 dorsal fin, the eye, the sides of the abdomen, and the 

 root of the tail. 



Nearly half the fish taken at La Nouvelle were thus 

 infested. At Port Vendres and Banyuls not more than 

 one in thirty or forty was attacked. At Rasccff there 



