66 BRITISH TYROGLYPHIim 



Nalepa, in the paper so constantly referred to in 

 this chapter, is probably the only author who has 

 described and figured the pharynx of any of the Tyro- 

 glyphidse correctly,* but reliable information as to 

 the form and construction of the organ in many 

 other families of Acarina is to be found in works by 

 MacLeod f for Trombidium, Hydrachna and Erythraeus, 

 by Croneberg J for Ei/lais, Henkin for Trombidium 

 fuliginosum, etc., Winkler || for Gramasidae, and by 

 myself for Thy as, ^ Bdella,** and Gamasus.^i The 

 description and figure given by Schaub for Hi/dro- 

 droma are in my opinion incorrect ; unless, indeed, 

 the pharynx of that creature be wholly different both 

 in position and structure from that of every other 

 Acarus that has been investigated; which scarcely 

 appears to be what might be anticipated having regard 

 to the very close relationship between Hydrodroma 

 and some of the creatures whose anatomy has been 

 studied by Croneberg and myself. 



What may be considered the typical form of the 

 pharynx in the Acarina consists of two more or less 

 chitinized half-tubes, like the gutter-pipes which run 

 under the eaves of houses, laid one inside the other; 

 both having the convexity downward, and running 

 longitudinally in the median line of the anterior portion 

 of the cephalothorax ; these two half -tubes are joined, 

 more or less flexibly, all along their lateral edges. The 

 lower half -tube is really a continuation of the floor of 



* Nalepa, Abtheil. i, pp. 198, 199, Taf. i, fig. 2. 



f " La Structure de 1'Intestin anterieur des Arachnides," in ' Bull. 

 Ac. Belgique,' 1884, Nos. 9, 10. 



J " On the Anatomy of Eylais extendens (Miiller), with observations 

 on allied forms," in Russian, in ' Trs. (Nachricliten) Soc. Nat. Moscou,' 

 1878. 



" Beitrage zur Anatoinie Entwicklungsgeschichte und Biologic 

 von Trombidium fuliginosum, Herm.," in ' Zeit. wiss. Zool.,' Bd. xxxvii 

 (1882), p. 569, Taf. xxxiv, figs. 5, 7. 



|| "Anatomic der Gamasiden" in ' Arb. Inst. Wien,' 1888, Bd. vii, 

 Hft. 3, p. 339, Taf. xx, fig. 15. 



Tf In ' P. Zool. Soc.,' London, 1895, p. 180, pi. ix, fig. 27. 



** In ' Tr. Linn. Soc.,' London, 1896, vol. vi, pt. 7, p. 485, pi. xli, figs. 

 1, 2 ; pi. xliii, figs. 3, 4. 



ft Ibid., vol. v (1892), pt. ix, pi. xxxv, fig. 73. 



