SEVENTEENTH ANNUAL EEPORT. 



395 



(2) Eyes (fig. 60) are not present in all forms. When present they 

 are visible as small, smooth, more or less semiglobiilar structures, one 

 on each lateral margin of the dorsal shield in the case of Ixodidae; or 

 punctiform structures on the supracoxal fold near coxae I, in the 

 Argasidse. 



(3) The doTSO-svhmedian jporose plates (fig. 61). — It is not yet deter- 

 mined how generally these are found in different forms, hut we have 

 observed them in the genera Dermacentor^ Bhipicephalus^^ Boopliihis^^ 

 and Ilycdomma.^ They are small circular or oval chitinous struc- 

 tures situated one on each side of the median line near the planes of 

 legs III and IV. Examined under a high power, they are seen to be 

 composed much like the stigmata of a ring which hi closes a number 

 of wart-like elevations, each of which bears on its summit an elongate 

 pore. The function of these structures is 

 not determined. They occur in both sexes. 



(4) The poster o-marginal festoons (fig. 

 169) are not present in all forms. When 

 present, eleven may usually be more or less 

 distinctly recognized. 



(5) The dorsal furrows (fig. 43) run lon- 

 Pfitudinallv and are due to the insertion and 



^ • /. 1 1 G6.— Tarsus I of Ornithodoros 



contraction of the dorSO-Ventral muscles. Jfe^mm with sense organ. Greatly 



They are not always distinct, changing with enlarged, original, 

 the repletion of the tick and with the muscular contractions. They 

 are described in great detail by some authors, who apparently attach 

 considerable importance to their arrangement. 



(6) Pits, punctations^ hairs ^ spines. — If a microtome section is made 

 through the cuticle of the tick, it will be seen that the tegument is 

 pierced by numerous pores, at the base of which are situated large, 

 peculiar gland cells, and from which issue hairs. On a surface view 

 these pores are seen as circular bodies of various sizes, and the hairs 

 or spines may be easily distinguished by means of a good hand lens. 



B. Ventral structures. — On the ventral surface are found: Gen- 

 ital pore, anus with anal valve, anal shields, ventral shields, stigmata, 

 furrows, or grooves, legs, pits, jnmctations, and haiTS. 



(1) The genital pore (fig. 62) is situated in the ventro-median line. 

 It is a transverse slit, more or less anterior, between the bases (coxae) 

 of the first three pairs of legs. It is not present in the hexapod larvae. 



(2) The anus (fig. 62), surrounded by a chitinous anal valve, is in the 

 ventro-median line, posterior of the last pair of legs. 



^ Bermacentor reticulatus; D. variegatus; D. electus; and D. nitens. 

 ^ Rhipicephalus sanguineus; R. bursa. 

 ^ Boophilus annulatus; B. australis. 

 ^Hyalomma segyptium. 



