198 PREPARATION AND MOUNTING 



eomplishing all that is desired. The tail is generally the 

 most transparent, and shows the circulation best ; but in 

 some of the newt larvae the blood may be traced down to 

 the very extremities if they are not too old. Mr. Whitney 

 places the tadpole upon its back, by which means the hearfe 

 and other internal arrangements may be seen. 



Amongst fishes also may be found subjects for the same 

 purpose, but they seldom furnish such good examples as 

 those before mentioned, because the blood-vessels are not 

 nearly so abundant as in the foot of the frog, &c. The 

 stickleback is, however, procurable almost in any place- 

 during the summer months, and may be laid in a shallow 

 trough, loosely bound down as the tadpole. The tail may 

 be covered with a piece of thin glass to prevent him curling 

 it to the object-glass. The power needed for this will be 

 about the same as with the other subjects ; riz., a half to 

 a quarter-inch object-glass. 



It is not absolutely necessary to go to reptiles or fishea 

 for this curious sight, as some other animals serve very 

 well. In the wings of the common 'bat may be found a 

 good subject. These must be stretched out on something 

 resembling the frog-plate before described, when those parts 

 near to the bones will show the largest vessels very clearly. 

 The ear of a young mouse is an illustration of the same 

 phenomenon, but it is very difficult to fix it in a good 

 position, as these animals are so very timid and restless. 



Amongst insects also the circulation may be seen by 

 placing them in the cage, or live-box, so as to keep them 

 still, but not to injure them by too much pressure. In 

 certain larvae it is particularly well shown, as in those of the- 

 day-fly and plumed gnat ; but in some of these the blood is 

 almost colourless. In the wings also of many insects this- 

 circulation is well seen, as in those of the common housefly ; 

 but as these parts become dry in a few days, the subject 

 should not be more than twenty-four hours old. 



Somewhat approximating to the forementioned pheno- 

 menon, is the rotation (or cyclosis) of fluid in the cells, 01?^ 



