202 STJBKINGDOM VERTEBRATA. 



ends only of any one of them. For instance, the shape of a single 

 finger-bone indicates the necessary form of the one with which it 

 articulates ; this latter its fellow, and so on through the series includ- 

 ing the metacarpal, carpal, radius and ulna, humerus, scapula and 

 clavicle. The result of this investigation suggests at once to a com- 

 parative anatomist the structure of the teeth, whether herbivorous or 

 carnivorous, and thus enables him to decipher the entire character 

 of the animal. Any bone in the series answers equally well for a 

 starting-point, and the skill of the investigator is shown in the readi- 

 ness with which he reconstructs the whole bony fabric from the 

 extremity furnished. Thus Cuvier, from single bones found in the 

 gypsum near Paris, drew the entire outline of fossil genera of mam- 

 mals ; and Agassiz, from isolated scales, restored the whole fish. (See 

 Geology, pp. 182 and 203.) 



HINTS FOR STUDYING REPTILIA, AMPHIBIA AND PISCES. 



In the latitude of southern New England during fifteen or twenty 

 days after June 10th, the smaller tortoises may be found about sundown 

 on the margins of the ponds and streams digging holes and laying their 

 eggs; the larger, as Ghelydrti serpentina, doing the same thing about 

 sunrise in the morning. Removing the eggs carefully without turn- 

 ing them over, they may be placed two or three inches deep in garden 

 sand, protected with net-work, kept moist, and so the progress of 

 embryonic development watched till they hatch in September or 

 October, by examining one egg at a time every two or three weeks. 



The Amphibia may be studied in a similar way by transferring frog 

 and toad spawn, found in streams about the first of June, to a glass 

 vessel of water containing sand and pebbles. It will be noticed that 

 frogs' eggs are in a glairy mass ; toads' eggs in a glairy string. If a 

 female newt be placed in the vessel with some growing aquatic plant 

 like spotted knot- weed (Polygonum persicarla), its curious habit of 

 folding a leaf in which to deposit its egg may be observed, and in 

 time all the changes pertaining to its metamorphosis. 



Large^ Reptiles, Amphibians and Fishes may be skinned and pre- 

 served according to the directions already given for Mammals and 

 Birds. Small specimens should be kept in alcohol, after making an 

 incision low down on the side, by simply inserting a penknife at as 

 small an angle to the surface as will permit the point to enter the 

 cavity of the abdomen. After a few days, alcoholic specimens should 

 be changed into fresh alcohol at least 80 proof. Glycerine may be 

 substituted for alcohol, when it is desirable to preserve the colors. 



