PHOTOGRAPHING BUTTERFLY EGGS. 11 



of the larger square, and press it down upon the smaller, so that the hole 

 is entirely filled up, and all is held firmly to the glass slip. Now 

 moisten a fine hair pencil between the lips and pick up a single ovum 

 on the point of it. Breathe upon the prepared gum surface within the 

 Jin. hole, and place the ovum lightly upon it. Continue the process 

 with as many ova as you wish to photograph at once, and they will all 

 be found to adhere quite as firmly as is necessary for the purpose in 

 hand, while they can be easily brushed off afterwards, and will be 

 none the worse for the treatment they have undergone. At least one 

 ovum of each species should be mounted upon its side, and it will then 

 be available afterwards to afford measurements otherwise unobtainable 

 from the resulting photograph. 



It is a very good plan to line the box, in which living £ s are put 

 for the purpose of obtaining ova, with paper, as then the ova will be 

 laid in most cases on the paper, and are easily accessible, whereas, if 

 they are laid directly on the sides of the box, these must either be cut 

 up or a thin shave taken from them to obtain the ova uninjured. 



The very worst material I know for photographic purposes on 

 which ova can be laid is cotton wool. Each individual ovum must be 

 separated from every strand of the wool before it can be mounted 

 with any hope of getting it to lie flat, or of placing the entire batch as 

 nearly as possible in one plane (a most important point to remember, 

 or your photograph cannot be in focus all over), while every strand of 

 the cotton which does get mounted with the ova, and there are sure to 

 be some, comes out like a piece of rope, and quite spoils the picture. 

 It is only necessary to try to manipulate ova so laid once, and you will 

 thereafter be very careful to ask all your friends, when sending you 

 any, to avoid getting them laid on cotton wool as they would avoid the 

 plague. 



It is unnecessary to go into any detail as to methods of developing 

 the negative after it has been taken, as these will vary with the make 

 of plate and the particular developer used, and are easily obtained 

 from the manufacturers ; but it is helpful to keep a full note with 

 each exposure of at least the name of species, magnification, lighting, 

 make of plate, exposure given, developer used, and colour and appear- 

 ance of the ovum. I write these particulars upon the outside of a 

 paper envelope, into which I afterwards slip the finished negative, 

 before storing it away, and I always pencil the name of the species 

 upon the corner of the plate before development, so that if it gets 

 separated from its proper envelope at any future time it can be 

 identified with certainty. The envelopes alluded to above should each 

 bear a consecutive number, and, if an alphabetical index to these is 

 compiled as they are made, any particular species required in future 

 can be found without loss of time. 



The exact amount of magnification is important, and once a con- 

 venient size has been fixed on, that, or multiples of it, should be 

 strictly adhered to, as otherwise any comparison will be difficult. An 

 easy method of ascertaining the magnification is to photograph a 

 finely ruled scale in place of the ova, and then compare your negative 

 with the original scale. 



