X INTRODUCTION. 



purpose of breedins^. At the commencement of the rains they become very excited, apparentlj^ unsatisfied 

 with the localities they inhabit, they restlessly seek a change. It is generally at this season that some have 

 been observed travelling on land, and it has been imagined that places which are only now and then covered 

 by water become peopled by tish in this manner after heavy showers of rain 



The modes of respiratiim in some of these fishes are exceedingly curious, and have a bearing upon 

 the question of migration. We find respiration carried on in three ways : — First, as is usually observed 

 elsewhere, oxyo-en is obtained from air in solution in the water and which is separated at the gills, as by carps 

 and most siluroids. If such fish have a bandage stitched round their gill-covers precluding the use of the 

 gills, they die owing to the impossibility of taking in oxygen as described : on the same principle if the water 

 becomes vei-y muddy their gills become choked, respiration impeded and death ensues.* Secondli/, we have forms 

 on which muddy water does not produce an injurious efiect on placing a bandage round the gdl-covers. They never 

 obtain oxygen for any length of time fi-om the air in solution in the suiTouuding water, but inspire it direct 

 from the atmosphere, no matter how cool and charged with air the water may be : if unable to inhale 

 atmospheric air they become poisoned by the carbon remaining in their circulation. Such fish are to be 

 found in the amphibious forms of Anahas (p. 369), Pohjacanthus (p. 371), Trichogaster (p. 373), Ophiocephalus 

 (p, 362), Saccobranchus (p. 486), etc. These fishes rise to the surface, expel a bubble of air, and at the same 

 time take in a fresh supply (see p. 439), and this mode of respiration enables them during periodic dry seasons 

 or in the rains to migrate from pond to pond in search of food, or to ascend small water-courses to breed 

 during seasons of inundation when the stream is frequently intermittent. Thirdhj, there are fish which 

 appear to swallow air, as the loaches and spined eels (Rhynchobdallid^, p. 338), but no special air-breathing 

 apparatus has as yet been detected, except that some species are stated to have portions of the intestines 

 lined with vascular papillfe, where oxygen is abstracted from air which is first swallowed and subsequently 

 returned by the mouth or by the anus. 



A curious phenomenon in Indian fishes is the appearance of adult and healthy ones after heavy falls 

 of rain in localities which had been dry for months previously. If when water failed in India, all the fishes 

 in tanks which dried up were to die, none would be found for the succeeding year's supply unless migrations 

 took place from other localities. As I and others have personally seen live fishes dug up from the ground 

 where a tank had dried up, I do not think we are justified in rejecting the native theory that they become 

 torpid in the mud where they wstivate. As the water in tanks becomes low, the fishes may be perceived 

 congregating in holes and places where their backs are barely covered : if disturbed, they dive down into the 

 thick mud so that a net is often inefi'ectual to capture them. As the water evaporates they become 

 increasingly sluggish, and finally there is every reason to believe that some at least bury themselves in the 

 soft mud and await in a state of torpidity the return of the next season's rains, as is weU known to be the 

 case in animals which possess a higher vitality, as Batrachians, some of the Crocodiles : also molluscs and land 

 snails amongst the invertebrata. It may be that ova of these fishes are in the mud of these tanks with 

 their germination retarded as we know can be accomplished by means of ice. However this may be, a few 

 days after the rains we find numerous fry in many inundated spots. 



The strictly fresh-ivater forms are divisible into those which are comparatively stationary or non- 

 tnigratory, and secondly the migratory forms which find the waters of the plains unsuitable for the deposition 

 of their ova, or else change their residence in order to obtain some peculiarly desirable description of food. 



We may, therefore, first briefly allude to the breeding of the non-migratory fresh-water forms of the 

 plains, some of which are monogamous others polygamous. The ubiquitous and amphibious walking fishes, 

 Ophiocephalidj;, are among perhaps the best known of the monogamous species, which as a rule do not produce 

 such a number of ova as the migratory forms, but appear to breed oftener. Some deposit their ova in tanks, 

 others prefer rivers where they live in deserted holes they find in the banks. When the fry are hatched 

 they are defended by their parents until old enough to protect themselves. The polygamous non-migratory 

 fishes of the plains are very numerous, and do not migrate any long distance for the purpose of breeding : 

 in places the smaller carps are innumerable. All these forms during the rains pass up small water-courses in 

 order to deposit their eggs in irrigated fields, flooded plains, temporarily formed tanks, or along the grassy 

 banks of flooded rivers. 



Of the migratory fresh-water fishes we have those which restrict their migrations to localities in 

 the plains and others which a.scend to hill streams to breed. These latter forms, as might be anticipated, 

 are as a rule larger and stronger than the non-migratory, and they appear to return to the hill ranges 

 to deposit their ova as naturally as some marine species enter fresh waters for this purpose. 



Of the Anadromous, or migratory marine forms which ascend rivers in order to deposit their 

 ova in suitable spots, we have a good example in the Hilsa or Shad {Clupea ilisha, p. 640). Weirs 

 now form an insuperable bar to their ascent up some of the rivers. 



The fry of the polygamous fresh-water fish have certain natural laws of protection. Thus they 

 are safe from their voracious parents in hill streams and rivers, as those localities being unable to supply 

 food to the mature forms they, having deposited their ova, drop down again into the rivers of the 



* If numerous fish are seen de.ad on the lianks of a flooiletl Indian river, it may be simply due to their gills having been 

 choked by mud : should any amphibious forms however be perceived, other causes must have been in operation as poison whether 

 introduced by man or the addition of water from jungles where it bad btcooje imprcguaied with poisonous vegetable substances. 



