AEAOHNIDA 265 



vol. xiv, p. 162. Blanchardj in ' Ann. des Sci. Nat./ ser. 3, 

 t. viii, and in f Kegn. Anim/ (with figs.). Oobbold, ' Entoz./ 

 p. 393 et seq. Idem, in f Quart. Journ. Med. Sci./ 1859, p. 205. 

 Idem ("P. cephalophi"), in ' Linn. Trans./ xxii, p. 357, and 

 xxiii, p. 350. Idem, in f Zool. Soc. Proc./ 1861, p. 124. 

 Diesing, ' Syst./ i, p. 609. Idem, ' Kevis. der Cephalocot./ 

 s . 327. Frerichs (1. c., in text), vol. ii, p. 276. Elob (und 

 Schroff), in f Gesellsch. d. Aerzte/ Wien, 1860. Kuchenmeister, 

 1. c., i, s. 370, Eng. edit., tab. viii. Idem (with Van Beneden), 

 in ' Bullet. Acad. Belg./ xxii (with figs.), 1855. Landon 

 (quoted in text). Leuckart, in 'Zeitsch. f. rat. Med./ 1857; 

 see also " Obs. on the development and early condition of the 

 Pent, tanioides" in ' Ann. Nat. Hist./ vol. iii, 3rd series, 1859 ; 

 also my translation of his " Further Observations on the 

 development of P. tanioides" from ' Henle and Pfeufer's 

 Zeitsch./ in the ' Quart. Journ. of Micr. Sci/ for 1859. Idem, 

 f Bau und Entwicklungsgeschichte der Pentastomen, nach Un- 

 tersuchungen besonders von P. tanioides und P. denticulatum,' 

 Leipzig, 1860. Moquin-Tandon, f Med. Zool/ (Hulme's edit.), 

 "The Linguatula," p. 329. Pruner (" Nematoideum ") in 

 ' Krankh. d. Orient./ 1847. Schubart, ( S. und K. Zeitschr./ 

 Bd. iv. Welch, see Bibl. No. 36. Zenker, in < H. und Pf. 

 Zeitschr. f. rat. Med./ 1854, s. 212 (with figs.). 



The ectoparasitic arachnidans comprise a great variety of 

 mites and ticks (Acarida and Ixodida) more or less proper to 

 man, and also a number of creatures which, though hardly to 

 be reckoned as human parasites, are apt to transfer themselves 

 from animals to man. Little more than an enumeration of the 

 forms is possible here. The Common Scab or Itch insect 

 (Sarcoptes scabiei) forms the type of a great variety of arach- 

 nids, generally spoken of as different species according to the 

 host they dwell upon. Megnin, however, in his beautiful 

 memoir, quoted below, regards most of the forms of this genus 

 (found on the horse, hog, sheep, dog, wolf, and other animals) 

 as mere varieties. In man the female Acarus burrows beneath 

 the skin, forming galleries or curved channels, in which she 

 deposits her eggs. The irritation produced is not alone due to 

 these excavations, but to the presence also of a poison which 

 the mite discharges when feeding. The Sarcoptes crustosae of 

 Fiirstenberg, producing the Norway itch, is a variety, if, 

 indeed, it can be called as much. Under the frightful na^e 

 Dermatophagoides Scheremetewshy two parasites foun 



