652 E. N. PAVLOVSKY 



of the integumental appendages of the larvae of H. cara- 

 boides. 



The greater part of the hairs are chaetoids, i. e. organs 

 developed exclusively from the chitinous cuticula ; the hypo- 

 derm under them does not show any peculiarities in its struc- 

 ture (PI. 27, fig. 7). 



The terminal (long) hairs of the pleural appendages are also 

 chaetoids, but they take their origin from a differentiated 

 terminal platform under whicli there are located large cells 

 with large nuclei. These cells are probably of a neural 

 character ; but this could have been proved only by applica- 

 tion of special methods of staining (with methylene-blue for 

 instance), which did not enter into the task of my work. 



The setae of the integument are distinguished by greater 

 length, stoutness, and stiffness (PI. 27, fig. 8). The base of the 

 seta is lodged in a chitinous cup-like tubercle (theca, ct) in 

 the interior of which is found a differentiated ring, which is 

 stained black by iron haematoxylin. Under this chitinous 

 armature lie two cells (fig. 8, etc), of which the larger one is 

 triehogenous and the smaller thecogenous. Together they 

 form a kind of follicle which invaginates into the cavity of 

 the body from a row of hypodermal cells. 



The setae described perfectly correspond with the type of 

 dermatochaetae, according to the classification of the integu- 

 mental appendages given by N. Nassonov (1901). In particular 

 they belong to the dermatochaetae plerothecatae (E. Pav- 

 lovsky, 1917), i.e. setae with a solid theca. 



Finally, the largest setae (PI. 27, fig. 9, on a pigmented base) 

 are distinguished by the most complicated structure. The 

 long chitinous rod (fig. 9, tCy) has its base set into a barrel- 

 like elevation of the integument. Into the upper part of this 

 barrel a short cylindrical cartridge (fig. 9, tc.2) is inserted, with 

 which, properly speaking, the seta is articulated. 



Under this formation there lie two large cells (fc), one of which 

 is distinguished by an enormous nucleus (the triehogenous cell) ; 

 in the protoplasm the borders between the nuclei are not 

 visible. 



