298 NOTES AND MEMORANDA. 



the contents of the glands were expelled with greater rapidity ; 

 totauization had a more marked effect, and produced changes in the 

 characters of the cells ; the most imjiortant of the chemical elements 

 found in the fully formed silk-thread was fibrous ; the yellow colour- 

 ing matter was observed to be formed in the cells of the median 

 portion, and it was also noted that the silk-threads did not exhibit 

 their special characters, or power of refracting light, unless they 

 were taken from the region in which the two efferent ducts were 

 found united. 



Odoriferous Cells in Lepidoptera. — The observations of Fritz 

 Miillcr on the attractive proi)erties possessed by the males of certain 

 LepidojDtera revealed the jireseuce of certain cells which seemed to 

 give off an odorous oil of the ether series ; the scaly cells to which 

 this oil owed its existence were never, however, found on the costce, 

 where, as it was imagined, the living cells of the wings were alone found. 

 Dr. August Weissmann now * points out that this last supposition is 

 erroneous, and that the other cells of the wing form a connected 

 network of irregularly-branched stellate cells, which are placed in 

 more or less closely set transverse rows below the scales, though they 

 can only be made out by the use of reagents. 



The scale itself is capillifoi-m, and traversed by a single axial 

 canal, which ojiens freely at the tip (as in Pajnlis protesilaus), or there 

 are a number of canals, which open on to the surface of the scale. It 

 is in the butterflic^s of Brazil or the Tropics that the odoriferous cells 

 are best developed, although indeed in Pieris napi it is quite easy to 

 convince oneself that the odour is given oft' from the scales, by passing 

 the finger over the wing ; the finger will be found to retain a strong 

 odour, not unlike that of citrons. In the closely allied species, P. rapce, 

 the same may be observed, but in it the odour is less strong and of a 

 different character. 



In connection with these observations of Weissmann, we may draw 

 attention to the communication which Fritz Miiller has made to his 

 bruther Hermann ; | he says that he finds his nose gets sharper in 

 detecting odours from butterflies ; thus, the male of Callidryas trite 

 was two years ago odourless, but he is now easily able to detect its 

 odour. In the male of Didonis hiblis he has now observed three 

 distinct odours in different parts. The females of Callidryas have 

 highly odorous glands connected with their generative organs, which 

 give off an acetous scent ; while the males of the same form have a 

 musk-like odour from the same parts. 



Seasonal Dimorphism of Lepidoptera. — Dr. Kramer makes some 

 elaborate computations J as to the modes by which this dimorphism, 

 the phenomena of which have been so learnedly treated by Professor 

 Weissmann, have been evolved ; a severely mathematical study leads 

 him to the following conclusions : — - 



1. By the cumulative action of transmission (heredity) a large 



* ' Zool. Anzeiger,' i. (1S7S) 98. t Ibid., 32. 



X 'Arch, fiir Natnrgeschichte,' xliv. (1878) 411. 



