222 BIOLOGICAL LECTURES. 



In performing an operation, a strong, very sharp cartilage- 

 knife was used. With a single clean cut a portion of a pupa 

 was cut away, and the remainder laid down with the wound 

 uppermost in order to prevent the escape of haemolymph 

 while the second component was prepared. The wounds of the 

 two fragments or components were then placed together, and 

 melted paraffine was applied to the edges with a camel's hair 

 brush. The paraffine on hardening formed a firm ring or band 

 which served the double purpose of keeping the component 

 parts together and of preventing the escape of haemolymph. 

 Wherever possible the operated complex was suspended in the 

 normal upright position, in cocoons cut to fit. 



When in the successful cases the imagines were ready to 

 emerge, a state indicated by the looseness and dryness of the 

 papery pupal shell, it was necessary in almost every instance 

 to pick off the shell with a forceps, bit by bit. A few moths 

 came out independently. In either case the freed moths were 

 put in a box lined with' netting, allowing them free room for 

 movement and expansion of their wings. Usually the wings 

 failed to expand to their full normal extent, probably owing to 

 the inevitable loss of haemolymph during the operation. Some- 

 times the wings of one component expanded, while those of the 

 other did not, depending apparently on the further development 

 of one beyond the other. 



No attempt was made to feed or rear the moths. After 

 being allowed to live a few hours or days, they were chloro- 

 formed and dried for total specimens or preserved in spirit. 

 For sectioning purposes some were preserved in Perenyi's fluid 

 and in Graf's chrom-oxalate mixture. 



The results fall naturally into three groups, according to the 

 operation and the relative size and make-up of the compound. 

 First, we shall consider those operations where portions of two 

 different pupae were united in normal proportions. In all 

 cases attempts to join lateral halves of two different pupae 

 were unsuccessful. Here the section passed sagitally a little 

 to one side of the median line. Although many of the com- 

 pounds lived in a plump, healthy condition for several weeks, all 

 ultimately died. 



