224 Da, R. BROOM ON THE OKGAX OF [Mar. 18, 



(?) The granules are especially well- developed upon the first 

 aiid second caudal segments and upon the last abdominal tergite, 

 against all of which the point of the sting can be forcibly scraped. 

 On the third caudal segment, upon which the sting is capable of 

 but little movement, they are scarcely or not at all developed, and 

 upon the fourth and fifth, which cannot be touched by the point 

 of the sting, they are absent. 



(4) The longitudinal flatness of the granular area on the fii-st 

 and second caudal segments, which resvilts from the uprising of 

 the groove and the elevation of the anterior part of the upper 

 surface, can be explained on the supposition that it is designed to 

 give the sting a long and continuous sweep fi'om segment to 

 segment, without the danger of catching against theii' posterior 

 edges or of wounding the arthrodial membrane. It is difficult to 

 see what other inteipretation is to be put upon this special and 

 unique modification of the segments in question. 



3. On the Organ of Jaeobson in the Elephant-Shrew 

 (Macroscelides prohoscideus). By R. Broom, M.D., B.&c} 



[Received February 4, 1902.J 

 (Plate XXI.^) 



From the examination of the organ ^ of Jacobs on in a large 

 series of mammals, I, in 1897, concluded that it varies surprisingly 

 little in even very dissimilar genera of a common Order. In the 

 Marsupialia the chief Polyprotodont genera have their organ of 

 Jaeobson veiy much alike, while even in the Diprotodonts the 

 orga.ns are all formed on a type which difl^ers but little fiom that 

 found in the Polyprotodonts. While in all the Rodents, so far 

 as examined, the organ is formed on a single peculiar type which 

 seems to be a modification of that found in the Marsupials, in the 

 higher mammals a single type of organ is found in forms so varied 

 as'the Hedgehog, Bat, Lemur, Cat, Sheep, and Pig. 



It would thus appear that the organ of Jaeobson is but little 

 influenced by the habits of the animal, that it remains a clear 

 indicator of the early family relationships of a genus when 

 almost all the other ancestral characters have been so modified 

 as to be scarcely recognizable, and that hence it is of consider- 

 able importance in determining the preci.se affinities of aberrant 

 mammals. 



Ha,ving recently had occasion to make a series of sections of 

 the snout of a foetal Elephant-Shrew {Macroscelides prohoscideus), 

 in connection with a study of the development of the palatine 

 process of the premaxDla, I was naturally much interested in 

 observing the condition of Jacobson's organ, especially as W. K. 



1 Commuiiicaicd by Prof. G. B. Howeb, F.R.S. 

 ' Foi' c\nb<iiutit>ii oj'tbc Plate, spo p. 227. 

 ^ Traus. K. Soc. Ediiib, vol. xxxix, p. 23-1. 



