710 Mr. T. H. Taylor on 



{Tupfehticpnci). In the simplest case the stigmatic area 

 on which the pits are grouped is flush with the cuticle. 

 Generally, however, the pits are carried on one or more 

 special budlike projections {Knospcn) of the skin which 

 contain prolongations of the felted chamber. In other 

 cases the base of the pitted stigma is produced into a horn 

 {ProtlioralMlhoi'ii) which contains a continuation of the 

 felted chamber, and carries the pitted stigma with its buds 

 at the end. The distal portion of the felted chamber 

 lying within the horn De Meijere distinguishes as the 

 felted chamher of the horn {Hornfilzhammer) and the 

 proximal part within the body as the Narhciifilzkammer. 

 A further complication is brought about by the formation 

 of a second pitted stigma on the felted chamber proximal 

 to the original one. The original stigma may then be 

 distinguished as the distal, and the second as the proximal 

 pitted stigma. The old spiracle, now closed, and the 

 adjacent new one together constitute what De Meijere 

 calls the compound sjnracle. The respiratory organ on 

 each side of the thorax of Dipterous pupie he regards as 

 a prothoracic pitted stigma, differing from the similar 

 organs of the larva and of the abdomen of the pupa 

 only in its greater size. In rare cases the pitted stigma 

 is absent and the respiratory function is performed by- 

 secondary structures (Chironomus). 



From this account it will be seen that the gill-apparatus 

 of the pupa of Simulium resembles the compound stigma 

 of De Meijere in the following particulars: (1) The 

 outer and inner stigmatic scars are connected by a solid 

 cord (Narhenstrang, De Meijere; initial thread, Miall). 



(2) From that part of the tracheal trunk lying proximal 

 to the inner stigmatic scar (spirach-chamher of the present 

 paper) a trachea with retiform markings {NarhenllhlMinrner, 

 De Meijere ; tracheal extension, Miall) passes to the respir- 

 atory organ {Prothorakalhorn, De Meijere ; tracheal gill of 

 many waiters; tube-gill, Vogler; cuticular gill of the 

 present paper). 



On the other hand the gill-apparatus of the Simulium- 

 pupa differs from the compound stigma of De Meijere in 

 the following respects : (1) The felted chamber of the 

 horn is absent. (2) Stigma-pits and buds are absent. 



(3) The connection of the gill with the tracheal extension 

 is made by means of a hollow cuticular ingrowth. From 

 these observations there seems no reason to resjard the 



