TURTLES. 179 



tanks, which are therefore usually restricted to zoo- 

 phytes, certain crustaceans, &c. The fishes which 

 seem to live in shallow water most readily are 

 the ballan and other wrasses, the rock goby, the 

 fifteen-spined stickleback, and several others. One 

 reason why fish will always be favourite objects 

 is the marvellous variety in their sizes, shapes, and 

 habits, in addition to their more intrinsic importance 

 as food. Many people never see anything but dried 

 fish, or stale fish exposed on stalls ; and these are as 

 different from the graceful objects seen moving about 

 in capacious tanks as the stuffed and labelled birds of 

 a museum are from the winged and animate choristers 

 of the woods ! 



The thin, worm-like lancelet (Amphioxus lanceolatus) 

 is kept alive at Sydenham, six of them coming from 

 Naples alive, in a post-letter! This little fish is not 

 more than a couple of inches in length, and is a 

 native of the Mediterranean. So singular is its inter- 

 nal structure (possessing neither brain nor vertebrae), 

 that an order had to be prepared by naturalists for its 

 separate reception. To zoologists it represents the 

 embryonic condition of fishes and mammals, in per- 

 manently possessing a notochord. The mud-fish (Pro- 

 topterus annectens} is shown at Brighton, and this object 

 is even more scientifically interesting than the lancelet, 

 as being a veritable " missing link " between reptiles 

 and fishes. It belongs to an ancient class, of which 

 the most remarkable living forms are now to be found 



N 2 



