lloyal Socictf/. 249 



attention. Ho had commenced his observations in Nicaragua with 

 the advantage of some previous knowledge of the subject, and was 

 tlierefore prepared to direct his inquiries to many points that required 

 elucidation before the Darwinian explanation of these phenomena can 

 be said to be established. Thus we find recorded his experiments on 

 living insects which are the objects of mimicry by other forms, as to 

 their distastefulness as food to insectivorous animals. Whenever he 

 observes an instance of mimetic resemblance, he reasons out its cxiuses 

 and conditions instead of merelj' stating it. One of the most striking- 

 cases he mentions is that of a green leaf-like locust, which almost alone 

 of all other living things stood its ground amid a destroj-ing host of 

 foraging ants. It stood immovable whilst the ants ran over its legs, 

 and allowed him to pick it up and replace it amongst the ants 

 without making an effort to escape. It might easily have flown, 

 away ; but it would then only have fallen into as great a danger ; 

 for the numerous birds that accompany the array-ants are ever on 

 the outlook for any insect that may fly up. Another case is that of 

 a Longicorn beetle, belonging to a genus the species of which re- 

 semble various other objects : those members of the genus which 

 live on dead wood are coloured so as to resemble lichen -stained 

 bark ; but one species (Desmij)hora fascicidata) resembles a brown 

 hairy caterpillar ; and this he found only on leaves. 



Mr. Belt's numerous observations on birds, as well as those on the 

 few mammals he met with, are marked by the same originality and 

 suggestiveness. His charming descriptions of the habits and haunts 

 of humming-birds will attract many readers besides ornithologists. 

 The use of the expanded white tail of the Florisii/ja mellivora in 

 courtship (p. 112), which he fortunately had opportunities of ob- 

 serving, will be a welcome fact to the partisans of the Sexual Selec- 

 tion hypothesis. The volume, besides, contains abundant contribu- 

 tions to the general physical geography of the country (his remarks 

 on the retrocession of the frontier of the virgin forest being especi- 

 ally worthy of attention) and to the ethnology of Nicaragua and 

 neij^hbourins: countries. 



PROCEEDINGS OF LEARNED SOCIETIES. 

 ROYAL SOCIETY. 



June 11), 1873. — William Spottiswoode, M.A., Treasurer and Vice- 

 President, in the Chair. 



" On the Structure and Development of the Skull in the Pig 

 {Sus scrofa)^ By W. K. Pakker, F.R.S. 



I have for some years past determined to concentrate my atten- 

 tion on some one type of Mammalian Skull, so as to be able to 

 present to the Royal Society a paper similar to those which have 



