4 SALT-WATER FISBES 



drawing up the lower lid, rather like the shutter of some cameras, 

 but the bass has no such power. The tope has curious arm- 

 like organs, known as " claspers " and associated with 

 reproduction, and it brings forth its young alive. The bass 

 has no such " claspers," and it deposits floating eggs, which are 

 fertilised in the water and which hatch out in the course of a 

 few days. Other examples might perhaps have been selected 

 from the sharks, even of our seas, which would at first 

 sight have presented a series of contrasts less striking. Thus, 

 had we chosen the rowhound (^Scyllium), we should have found 

 that it so far resembled the bass in depositing eggs and in 

 being unable to close the eye. Had the blue shark been 

 selected as the type of cartilaginous fishes, we should have 

 found no distinguishing spiracles on the head to assist the 

 breathing of the gills. In the main, however, the two fish 

 above named serve the purpose of contrasting the two groups, 

 the bony and the gristly. The former, as already mentioned, 

 include practically all our table-fish — the cod, salmon, sole, 

 whiting, mackerel, herring, eel ; the latter comprise among 

 eatable fishes only a few rays and, in addition, all the largest rays 

 and fiercest sharks. These scavengers of the ocean scour every 

 depth in search of dead or living prey, the sharks for the most 

 part near the surface, the rays at the bottom. To this rule 

 there are, however, well-marked exceptions, for many of the 

 largest sharks prowl at the bottom, while some of the giant 

 rays feed close to the top of the water. 



It is not intended that the systematic classification of fishes 

 shall occupy many lines of the present chapter. Not too 

 much importance need be attached to even the latest recog- 

 nised arrangement, that of Mr. Boulenger in the Cambridge 

 Natural History, though perhaps more excellent than any of 

 its predecessors. The fact is that the systematic grouping of 

 fishes, like that of birds, is subject to somewhat frequent 

 modification. Nature knows no such abruptly demarcated sub- 

 orders and families and genera, which are, with their scientific 



