292 Dr. H. Eltringham on 



taken place immediately after the first, and whilst the first 

 secretion was in a more or less viscous condition." That 

 it is only produced by pairing is certain, since bred females, 

 of which we have hundreds of examples at Oxford, never 

 show the structure in question. In face of this fact it is 

 difficult to understand why Professor Houlbert should have 

 written, " Quant a l'origine meme du sphragis nous n'avons 

 pas en ce moment, de donnees assez precises ; mais nous ne 

 desesperons pas de l'expliquer le jour 6u il nous sera permis 

 de suivre revolution de quelques Acraea vivants. Dans 

 tous les cas, nous ne pouvons pas accepter l'opinion des 

 auteurs qui considerent le sphragis comme le resultat 

 d'une secretion deposee par le male sur l'abdomen de la 

 femelle au' moment de l'accouplement." 



Professor Houlbert expresses the opinion that the 

 sphragis, owing to its perfect adaptation to the shape of 

 the male armature, ensures the precise and unerring action 

 of those complicated organs. It seems not to have oc- 

 curred to him that the exact correspondence in shape 

 between the sphragis and the male armature is due to the 

 same cause which governs the correspondence between 

 the plaster cast and its mould : the one has taken its shape 

 through intimate contact with the other. 



Two further points remain. Professor Houlbert on 

 p. 152 expresses the opinion that the sphragis is an organ 

 of adaptation, and that after pairing it falls off, and the 

 female genital plate being thus uncovered, the eggs can be 

 deposited, without hindrance, on the plants which are to 

 sustain the larvae. 



Now, in the first place, the sphragis does not fall off under 

 normal conditions. It is found on the parent Acraeas in 

 the Hope collections at Oxford, from which were bred long 

 series of examples. Secondly, there is no necessity for its 

 removal, since the external opening of the oviduct is not 

 the same as the copulatory opening, but occupies a posterior 

 position. The insect would be in no way inconvenienced 

 in the matter if the copulatory orifice were hermetically 

 sealed for the rest of its life after pairing. This fact of 

 butterfly anatomy has doubtless escaped Professor Houl- 

 bert's notice. The remaining point with which I must 

 deal is the statement on p. 158 that the uncus of the male 

 is more highly developed in those species whose females 

 are found to bear a sphragis, and is very small in cases 

 where the genital plate is reduced or absent. In very 



