680 Dr. T. A. Chapman on Asi/inviclnj in 



developments would no doubt prove to afford an important 

 part of the data. 



Why asymmetry of the central organ should be so 

 common in the group and "not have passed to the other 

 parts except in the one minor subfamily of ILrniarime I do 

 not know, it is not impossible that it has in iact done 

 so, in cases of which I liave no knowledge. 



I cannot help thinking that in the LepidopTERA asym- 

 metry of the ledosagus is probably really very much more 

 frequent than we imagine. Unless exceedingly pro- 

 nounced, the two commonest ways of mounting the 

 appendages for examination would probably lead to its 

 being entirely overlooked. One is to mount the parts on 

 a glass slide, the other to separate the parts and mount 

 each separately on a card or mica slip. In either of these 

 ways the precise orientation of the isdceagus would be very 

 likely, if not certain, to be lost, and the opening really 

 existing on the ri^ht side of the tube would be believed to 

 be below, and any azygos appendage of the left side would 

 be assumed to be dorsal (or possibly ventral). The 

 Sphinges are so large that there is no difficulty in preserv- 

 ing the specimens in their natural positions (approxi- 

 mately), and examining them so. Even in Fapilio, how- 

 ever, in which Gosse apparently followed this plan, he 

 appears to have met with some unilateral deviations, which 

 he explained away as merely apparent and probably due 

 to rotation of the tube on its axis. 



In the Hemarinie, where the asymmetry affects the 

 valves, and more especially their inner spines (harpes), the 

 nature of the asymmetry is different from that obtaining 

 in the genus Thanaos. In the first place Scudder makes 

 no mention of the xdceagus, which one assumes therefore 

 to be symmetrical. The remarkable differences in the 

 valves of the two sides, strike one as being complementary. 

 The work to be done on either side is precisely the same 

 as that on the other, and neither valve is definitely larger 

 or smaller, more twisted one way or other, than the other 

 one. The object would appear to be, not only to do its 

 own work better, but to assist the valve of the other side 

 in doing the same, just as in the much simpler apparatus of 

 a catch forceps, the teeth on the two sides differ, not to 

 perform different functions, but really identical functions 

 more efficiently. 



In Hemaris, the two sides differ by actual diminution 



