REPTILES, BATRACHIANS, AND FISHES. 49 



near the eyes, where they are sometimes of a pinkish or greenish 

 colour. These are the so-called phosphorescent organs ; and 

 although their luminous properties are now generally admitted, 

 it is desirable to obtain corroborative evidence as to their function 

 from the living fishes, with special reference to the question whether 

 the luminosity is subject to the will of the fish. 



Labelling of Specimens. 



It is most important that every specimen should bear an indication 

 of the place, date, and circumstances under which it was collected, 

 as well as the native name, if it can be ascertained. This is best 

 done by keeping a notebook or diary, in which the entries are made, 

 each entry bearing a number corresponding to a label attached to 

 the specimen. Threaded parchment labels, a quarter of a square inch 

 in size, are most suitable for the purpose, the numbers being inscribed 

 beforehand in ink, which, when allowed to dry well, will not run 

 when immersed in the spirit. Pencil-marks are liable to become 

 illegible through rubbing off. In the case of fishes a second label 

 may be inserted under the left gill-cover, as a precaution in case 

 the threaded label should become detached and lost. 



