Fishes. 



6455 



tary functions of breathing, &c, may be supposed to have been per- 

 formed in a somewhat natural manner. The first character in this 

 function that struck me as worthy of comment was the extreme 

 regularity of the rythmical inspirations. I had not the opportunity, 

 on either occasion of observing the fish during anything like an entire 

 minute ; its motion was incessant, but T marked the internals of 

 inspiration by a watch, and although, in many instances, the obser- 

 vation extended to but three inspirations the measurable recurrence 

 of the act was established beyond a doubt ; the conclusion resulting 

 from observations made during twelve consecutive minutes being, 

 that the creature inspired water thirty-one times per minute. On the 

 occasion of another visit, a second set of observations was made with 

 equal care, and a somewhat different result obtained, the average 

 number of inspirations being thirty-three per minute : hence it must 

 be admitted that, in a state of confinement, in a limited quantity of 

 water, and with an atmosphere heated to 70° Fahr., the mud- fish 

 breathes once in two seconds, and it may be inferred from the vigour 

 and activity displayed by the animal, and from its enormous increase 

 in size, that this rate is that of health, and not the result of peculiar 

 circumstances. These inspirations differed very considerably from 

 those of the gold-fish, inasmuch as the interior fleshy substance con- 

 tained between the rami of the lower jaw rose after each inspiration, 

 and being pressed against the palate, entirely precluded the return of 

 the water through the mouth. This mode of breathing I subsequently 

 found was that of the Esocidae, and is beautifully exemplified by a 

 pike in one of the tanks at the Zoological Gardens. His extreme 

 quiescence greatly facilitates the observation. I failed to observe the 

 characters of the external aperture, or gill-opening, but of the existence 

 of such an aperture there could be no doubt, for I saw, after every 

 third or fourth inspiration, a number of minute bubbles, having exactly 

 the appearance of globules of quicksilver, escape in front of the anterior 

 tendril, and ascending to the surface of the water there become amalga- 

 mated with the atmospheric air : the number of these globules was 

 usually five or six, sometimes seven or eight : one or two were always 

 larger than the rest, but still minute, and likely to escape the notice of 

 a hasty or superficial observer. During the two visits the creature 

 never once ascended to the surface, but frequently ascended almost 

 perpendicularly towards the surface, and before reaching it altered his 

 course and turned downwards among the weeds : this observation, 

 probably made prior to Dr. Gray's, is exactly corroborated by him. 

 " It often rises with its body perpendicular," writes Dr. Gray, " as if 



