100 Gossip about Fish. 



most popular, because the apparently simplest, method of 

 observation and philosophizing, every animal, for example, is 

 supposed to be gifted with a special structure, in order r that it 

 may live under particular conditions and perform particular 

 acts. According- to another method of reasoning, the structure 

 is the result of general laws operating under special con- 

 ditions, and each animal belongs to a group, the whole of which 

 must be studied before the individuals composing it can be 

 understood ; while the entire group has definite relations to 

 other groups, and so on throughout the whole round of nature, 

 which forms one great unity, in which Creative will and in- 

 telligence are displayed in conformity with an all- comprehending 

 plan. Which ever mode of reasoning the tendencies of par- 

 ticular minds may lead them to adopt, the relation of habit to 

 structure, or of structure to habit, is equally important ; the 

 difference being that the more philosophical and wider of the 

 two systems give a proportionately ampler signification to every 

 iact that is ascertained. 



The fish, the reptile, and the bird, at first sight so different 

 in appearance, and so apparently separated by a great gulf in 

 structure as well as in habit, are found to grow nearer to each 

 other the better they are understood. 



Professor Huxley divides the vertebrate animals into three 

 .ascending groups; (I.) the Ichthyoids, comprising fishes and 

 amphibia, defined by the presence of branchiee or gills at 

 .some period of existence, nucleated blood corpuscles, and 

 certain other peculiarities ; (II.) the Sauroids, which have no 

 branchiae or gills at any period of their existence, nucleated 

 blood corpuscles, certain peculiarities in the skull, and other 

 ^structures, and which comprise reptiles and birds ; and (III.) 

 the mammalia.* 



It is by tracing points of resemblance of too technically 

 ; anatomical a character to be referred to in detail in this place, 

 that Professor Huxley expresses the decision of comparative 

 .anatomists, when he speaks of the class of birds as " an ex- 



* The passage stands as follows: — "The vertebrata are capable of being 

 grouped into three provinces : (I.) The ichthjoids (comprising fishes and 

 amphibia) defined by the presence of branchiae at some period of existence, 

 the absence of an amnion, the absence or rudimentary development of an 

 allantois, nucleated blood corpuscles, and a parasphenoid in the skull. (!!•) 

 The sauroids defined by the absence of branchia; at all periods of existence, 

 the presence of a well-developed amnion and allantois, a single occipital 

 condyl*, a complex mandibular ramus articulated to the skull by a quadrate bone, 

 nucleated blood corpuscles, and no parasphenoid, comprising reptiles and 

 birds ; and (III.) the mammals devoid of branchiee, and with an amnion and 

 an allantois; but with two occipital condyles and no parasphenoid ; a simple 

 mandibular ramus articulated with the squamosal and not with the quiidratum 

 with mammary glands, and with red non-nucleated blood corpuscles." — Elements 

 of Comp. Anat., p. 74. 



