ON LABELING SPECIMENS AND TAKING NOTES. 321 



sects both a note-book and loose sheets of paper are 

 used. 



The species on which observations are made are 

 numbered, as described on page 317. The note-book 

 is a paged blank book, which is made of ruled quarto 

 paper. There is a single red line about one inch 

 from the left margin of each page. An entire page 

 is devoted to each number ; this greatly facilitates the 

 finding of notes, for the number of the notes and that 

 of the page are the same. The space at the left of 

 the red line is reserved for dates and subnumbers. 

 The first line of the notes consist only of the name of 

 the species ; if this is not known at the time the notes 

 are begun, the line is left blank and a descriptive title 

 for temporary use is written on the second line. 



As already stated, one page of the note-book is 

 reserved for notes on each species. In many cases 

 this page is sufficient ; when it is found insufficient, 

 the expression " See notes " is written at the end of 

 the note in the book, and all further notes are written 

 on loose sheets. These are kept in folded sheets of 

 Manilla paper, which are stored in boxes in their 

 numerical sequence. 



The use of a note-book in this system is a sure 

 protection against the danger of using the same 

 number twice ; and it is the most convenient method 

 of keeping the notes on the large number of species 

 respecting which extended observations are not made ; 

 while the supplementary sheets afford all the advan- 

 tages of the slip system when extended observations 

 are made. 



Indication of Sex. — In many insects there are 

 marked external sexual differences, either of size, 



