SELECTED NOTES. 177 



organs of touch, and may be seen very distinctly in a vertical 

 section of a well-distended proboscis (see Fig. 4). 



Another feature well developed in the third joint of the 

 antennae of the Blow-fly, and many of the other domestic species 

 of flies, is a somewhat spiral organ covered on the exterior with 

 fine impregnated hairs; these hairs penetrate the wall of the 

 organ, which is also lined on the interior surface with epithelium 

 and receive a rich supply of nerve-fibres. It is computed that 

 there are about eighty of these organs in the one antenna of the 

 Blow-fly, and from their position, and the well-known highly deve- 

 loped sense of smell possessed by this insect, there can scarcely 

 be a question but that they are olfactory. The extreme paucity 

 of these organs in other species of different habits strengthen my 

 convictions on this subject. Among these are the common Dung- 

 fly, Eristalis tetiax^ Rhingia rostata, and a host of others. 



Eristalis tenax, longitudinal section of haltere.— For conven- 

 ience of examination the haltere of the fly may be divided into 

 three separate parts — viz., base, pedicel, and globe or head. On 

 the exterior surface of the base there are three distinct areas or 

 sets of sense organs, which severally have an anterior, posterior, 

 and lateral aspect. These have long been considered to be special 

 sense organs. The lower area is somewhat rounded on the face, 

 and covered with delicate elevations of the epidermis, which take 

 the form of circular papillae. They are divided into rows, and 

 between each row there is a line of curved hairs. Lowne states 

 that there are two distinct sets of these lower organs, and Theo- 

 bald, in his new work on British Fiies, has repeated this statement ; 

 but in no instance have I met with more than one, and it has 

 invariably a lateral aspect. The two upper organs are placed on 

 opposite sides of the haltere — one anterior and the other posterior. 

 They are much longer and larger than the lower one, but are like 

 it in having rows of ridges beset with papillae^ separated by fine 

 hairs. 



Several sections show the lining epithelium remarkably well. 

 In this place it is specially modified to form a sensory or nerve 

 epithelium. The pointed ends of the cells are seen penetrating 

 the papillae of the lateral organ. The halteres receive their rich 

 supply of nerves direct from the second thoracic ganglion. This 



