ARTHROPODA 



LITERATURE. 



349 



MoyuiN-TANDON. Monogr. cle la fam. des Hirudinees, 2nd edit., Paris, 1846. 



EBRARD. Nouv. monog. des sangs. medic. Paris, 1857. 



WHITMAN, C. O. The external morph. of the Leech. (Proc. Amer. Acad. of Arts 



and Sc., 1884, xx., p. 76.) 



The Segm. Sense Organs of the Leech. (Amer. Naturalist, 1884, xviii., p. 1 104.) 

 The Leeches of Japan. (Quart. Journ. of Micr. Sc., 1886 [2], xxvi., p. 317.) 

 APATHY. Analyse d. auss. Korperf. d. Hirudineen. (Mitth. d. zool. Stat. Neapel 

 1888, viii., p. 153.) 



Siisswasser-Hirudineen. (Zool. Jahrb. Abth. f. Syst 1888^.725.) 



BLANCHARD, R. Art. Hirudinees. (Dist. encycl. d. sc. Med., 1888, xiv., p. 129, and 

 C. R. soc. biol., Paris, 17 Oct., 1891 ; as well as in Bull. soc. zool., France, 

 1890-99.) 



LEUCKART, R. D. Paras d. Menschen. (2nd edit., i vol., ii., Hirudineen continued 

 by G. Brandes. Lpz., 1886-1901.) 



F. ARTHROPODA. (Jointed-limbed Animals ) 



Bilaterally symmetrical segmented animals which 'are covered with a 

 thick cuticle that is frequently calcareous (crustacea,), but always thinner 

 between the segments ; they carry (primitively) a pair of jointed appendages 

 on every segment. 1 The segments of the body are uniform in certain 

 regions, but differ from those of contiguous regions, so that it is easy to 

 distinguish three parts (head, thorax, and abdomen), each composed of 

 segments. The cephalic segments are always formed into an uniform head, 

 the segmentation being scarcely recognisable at either end ; the thoracic seg- 

 ments may also fuse, or part or all of them may coalesce with the head ; 

 the abdomen, as a rule, retains its segmentation ; but this may possibly also 

 be lost, in which case it is [sometimes, F. V. T.] united to the cephalo- 

 thorax. The structure of the three regions depends mostly on the varying 

 form and function of the appendages those on the head are primitively 

 locomotive organs (and frequently are still so in the early stages), but 

 they become transformed into feelers and mouth-parts (mandibles, maxillae) ; 

 the limbs of the thorax, however, usually retain their ambulatory func- 

 tions, as frequently do those of the abdomen ; sometimes, however, the abdo- 

 minal limbs disappear, entirely or partly ; in the latter case they are then 

 utilised for other purposes. 



In their organisation the Arthropoda approach to the segmented worms. 



The Arthropoda are generally divided into five groups (Crustacea? Pro- 



1 [In most Arthropoda the skin is hardened by a deposit of chitin (Hexapoda, &c.). 

 F. V. T.] 



- Parasitic or free-living crustaceans may now and then invade man abnormally. 

 Thus, according to Betten, Caligus curtus invade the cornea (Betten, R. A., " Par. Crust 

 as a Foreign Body on the Cornea," Lancet, 1900, i., p. 1002 ; and Centralbl. fur Bakt. t 

 Paras, u. Infekt., xxix., p. 506). According to Laboulbene, Gammarits pulex (Laboul- 

 bene, A., " Obs. d'accid. caus. par le G. pul. apport. avece I'eau de boison dans Vestomac 

 d'un'homme," Bull. Ac. mfd., 1898, p. 21). 



