384 THE POPULAR SCIENCE MONTHLY. 



assort them in accordance with those characteristics ; in short, to ar- 

 range or classify them. The young conchologist, for example, sees in 

 an instant that out of a miscellaneous collection of shells some are 

 bivalve and others univalve, and that some of them exhibit clear dis- 

 tinctions connected with the form of the animal to which the shell 

 belongs. The young entomologist, with still greater ease/ perceives 

 the difference between most of the insects that come in his way, and 

 indeed in some cases needs no instigation to look for them the differ- 

 ence between a grasshopper and a house-fly, a beetle, a butterfly, and 

 a moth, being self-evident to any one with eyes. So with the verte- 

 brates ; it requires no previous zoological instruction to enable any 

 child to point out characters that will separate a snake from a tortoise, 

 a rabbit from a sheej), a whale from a camel, and the rough primary 

 division of all these creatures is at once perceptible. But with fishes 

 this is not so. The learner, judging, as he is at first inclined to do, 

 from outward survey, is surprised to find that the essential differences 

 between a lamprey and an eel are deemed to be far greater than 

 between an eel and a salmon, and that a skate is much further re- 

 moved from a turbot than the latter is from a gudgeon, while a lance- 

 let, which, when immersed in a bottle of spirit, looks so like a small 

 smelt, differs, in the opinion of certain systematists, more from it than 

 the smelt does from a frog, or indeed from any other existing verte- 

 brate. All this, which the learner finds written in the first book on 

 the subject (if he has one of the least authority) to which he has ac- 

 cess, is so entirely in contradiction, as he thinks, to the plain evidence 

 of his eye-sight, that he may well be staggered at the outset of his 

 studies and discouraged from their prosecution. The classification of 

 fishes has in truth been a task of no ordinary difficulty, and it is a sub- 

 ject requiring a far greater knowledge of their internal structure than 

 can possibly be expected of a beginner. 



One of the most formidable difficulties in the way of arriving at 

 an intelligent classification has been removed by a discovery which 

 Dr. Giinther has made concerning the affinities of certain groups of 

 fishes or fish-like animals, the relations of which to each other and to 

 other fishes had been an inscrutable puzzle to all systematists. Among 

 these were the ganoids, a family represented in an indefinite number 

 of fossils, mostly of very ancient date, but few types of which survive 

 to this day, and these restricted to the fresh waters of Eastern Asia, 

 North America, and tropical Africa ; other fossil fishes of equal an- 

 tiquity, which were closely allied to the abundant sharks, dog-fishes, 

 rays, and skates of our own seas, the " Chondropterygians " or " Elas- 

 mobranchs " ; sturgeons, " Chondrosteans," possessing much of an 

 archaic character ; and besides these, there now exist two animals, 

 commonly called " mud-fish," scientifically " Dipnoi," which have been 

 deemed by some great authorities true fishes, by others amphibians. 

 Furthermore, in the early days of the settlement of the Australian 



