Structure of Scent Organs in Male Danaine Butterflies. 165 



of the greatest value in enabling us to learn something of 

 the function of the scent-pocket. We may, I think, fairly 

 assume that the vacuolated cells form the glands which 

 produce the oily secretion, and that this is accumulated in 

 the scales and discharged thence into the wing-pocket. 

 There remains then the dust material which occurs in such 

 large masses in the pocket, and can also be observed en- 

 tangled in the hairs of the anal brush. I was for some 

 time at a loss to discover the true origin of the dust fila- 

 ments. In my sections of the scent-pocket they were 

 invariably found loose in the cavity and already much 

 broken up. I found the same substance, but in a still 

 more disintegrated condition, amongst the hairs of the 

 abdominal brush. In the brush there was no evidence of 

 dust production, whilst its presence in larger quantities 

 and in a less pulverised condition in the scent-pocket 

 strongly suggested the latter as its place of origin. 

 Probably the truth of the matter would still have re- 

 mained a mystery, but for my having been fortunate 

 enough to secure, through the kindness of my friend 

 Prof. Poulton, a pupa of T. limniace, the oriental form 

 of this species, in which the imago was almost com- 

 pletely formed. The specimen had been sent to the 

 Hope Department from Ceylon by Lieut. -Col. N. Manders. 

 The pupa was not preserved in any way, being merely 

 dried, and I had small hope that sections of any value 

 could be cut from it, but the inspiring optimism of my 

 friend above mentioned was quite justified. A prolonged 

 evaporative embedding in celloidin resulted in my being 

 able to cut sections which revealed the highly interesting 

 fact that the dust filaments are produced beneath the 

 pupal covering, and that, by the time emergence takes 

 place, the cells from which they arose have become prac- 

 tically atrophied. The examination also showed that up 

 to the time of emergence there is no scent-pocket at all. 

 The area which subsequently becomes a pocket is, as in 

 the Amaiiris imago, a patch on the hind-wing. In Tiru- 

 mala, however, the expansion of the wing after emergence 

 causes an invagination of the patch, which thus becomes 

 a pocket. In dissecting out the wing from the dried pupa 

 already mentioned I found that the patch was covered 

 with a rather thick mass of material, which in its dry state 

 scaled off and fell to pieces at the least touch. This sub- 

 stance mounted in clove oil proved, as was expected, to 



