2690 FISHES 



(Aspredo), where they are pressed into the skin of the under surface of the body, 

 and a pipefish {Solenostoma) , where they are carried in a pouch formed by the coa- 

 lescence of the broad pelvic fins with the skin of the body, is the female known to- 

 take any care of her eggs after spawning. Among the bony fishes there are, how- 

 ever, several instances where the young are more or less carefully tended by the 

 male parent; some, like the sticklebacks, building a nest, while others, like certain 

 pipefishes, have an abdominal pouch in which the eggs are hatched. The eggs of 

 sharks, rays, and chimseroids differ remarkably from those of bony fishes, being 

 large in size, few in number, and laid singly instead of in masses. They are in- 

 vested in a hard horny envelope, which is generally oblong in form, with the four 

 corners produced, and frequently elongated into tendrils by means of which the egg 

 is moored to some foreign substance. The males of these fishes are armed with or- 

 gans known as claspers, which are partially ossified processes arising from the pubis, 

 and are evidently connected with the function of reproduction. The young of many 

 fishes differ markedly from the adult; and certain peculiar creatures with long 

 ribbon-like bodies and small heads, for which the name of Leptocephali has been 

 proposed, are believed to be the young of littoral fishes which have been carried out 

 to sea, where they have undergone an altogether abnormal development. The 

 changes which take place in the flat fishes during development may be more con- 

 veniently noticed under the heading of that group. Although male and female rays 

 differ remarkably from one another in the structure of their teeth, while both in 

 this group and in the sharks and chimaeroids the males are distinguished by the pos- 

 session of the aforesaid claspers, there is generally but little sexual difference among 

 fishes. In the bony fishes, however, the females are larger than the males; among 

 the cyprinodonts the difference between the two being occasionally as much as six 

 times. 



Fishes exhibit a remarkable degree of difference in regard to theii 

 enacity of power o f bearing changes from their normal environment. On this 

 subject Dr. Gunther writes that, "some will bear suspension of respi- 

 ration caused by removal from water, or by exposure to cold or heat for a long 

 time, while others succumb at once. Nearly all marine fishes are very sensitive to 

 changes in the temperature of the water, and will not bear transportation from one 

 climate to another. This seems to be much less the case with some fresh-water 

 fishes of the temperate zone; since carp may survive after being frozen in a solid 

 block of ice, and will thrive in the southern parts of the temperate zone. On the 

 other hand, some fresh-water fishes are so sensitive to a change in the water that 

 they perish when transferred from their native river into another apparently offer- 

 ing the same physical conditions. Some marine fishes may be abruptly transferred 

 from salt into fresh water, like sticklebacks; others survive the change when grad 

 ually affected, as many migratory fishes; while others, again, cannot bear the least 

 alteration in the composition of the salt water (all pelagic fishes). On the whole, 

 instances of marine fishes voluntarily entering brackish or fresh water are very nu- 

 merous, while fresh-water fishes proper but rarely descend into salt water." 



The foregoing remarks lead naturally to the subject of the distribution of 

 fishes, a subject which the limits of space compel us to dismiss with a few sentences- 



