female has a tubercle on the head, whilst the male has none, though 

 furnished instead with a pair of horns on the lower surface of the thorax. 

 Another case mentioned last year at a meeting of this Society shows that a 

 female insect may have a decided frontal hoi'n whicli is entirely wanting in 

 the male. (Proc. Ent. Soc, 1877, xvii.) 



" As the theory we are examining is not limited to insects, I may perhaps 

 be permitted to point out that if it were in accordance with facts, such 

 secondary sexual characteristics would be less striking in the males of 

 polygamous birds and mammals than in those of monogamous species, and 

 would be increased by emasculation — the very reverse of what is actually 

 observed. 



" Duly weighing such facts, I think we are driven to the conclusion that 

 the theory of horns and similar projections and enlargements being mere 

 excretory growths — means of getting rid of certain refuse matter supposed 

 to be coimected with the male sex rather than with the female, and with a 

 vegetable rather than with an animal diet — is utterly inadmissible. It would 

 perhaps be nearer the truth were we to say that these horns, crests, &c., like 

 the higher and brighter coloration so common in the male sex were the 

 result of a more intense vitality. 



" Another theory proposed is that nocturnal habits promote what may be 

 called monstrous developments of different parts of the system. But to 

 this view we may at once take the preliminary objection that nocturnal 

 habits should have a similar effect upon both sexes. It must be, 

 indeed, admitted that a far larger proportion of species are provided with 

 horns and ridges among the DynastidcB and ScarabcBidcB than among the 

 diurnal CetoniidcB. But, on the other hand, there are abundance of nocturnal 

 groups in which these secondary sexual characters are altogether wanting. 



" Are they ornaments attractive to the females, as seems to be the opinion 

 of Mr. Darwin, and are they a result of the action of 'sexual selection'? 

 It must be remembered that in many of the horned Coleoptera the growth 

 of these parts varies extremely. In Oryctes nasicornis there are males in 

 which the horn is so completely obsolete that they might be regarded as 

 specifically distinct from the long-horned type, if we had not a complete 

 series of intermediate forms filling up the interval. I never, indeed, noticed 

 that the hornless or short-horned males seemed less acceptable to the females 

 than were their long-horned contemporaries. Nevertheless Mr. Darwin's 

 view seems certainly less open to objections than the theories I have already 

 mentioned." 



New Part of ' Transactions.' 



Part V. of the 'Transactions' for 1877, containing index, title-page, ic, 

 was on the table. 



