LINGUATULIDA. 487 



the abdomen. Special copulatory organs in the region of the genital 

 openings are, as a rule, wanting, but appendages far removed from 

 the genital openings (e.g., pedipalpi of Spiders) often serve to transfer 

 the sperm from the male to the female. The female sexual organs 

 are also paired, usually racemose glands, with two oviducts, which 

 usually dilate to a receptaculum seminis before their single or double 

 opening at the beginning of the abdomen. They are also connected 

 with accessory glands. Rarely (Pludangiuiii) there is a long pro- 

 trusible ovipositor. 



Only a few of the Arachnida are viviparous (Scorpions and some 

 Mites) ; the greater number lay eggs, which they sometimes carry 

 about with them in sacs till the young are hatched. As a rule, the 

 just-hatched young have the form of the adult ; but in most Mites 

 two or more rarely four legs are wanting, and appear only with the 

 succeeding moults. The development of the Pygnogonida Pentas- 

 tomida and Hydrachnea (water-mites) (which latter pass through a 

 pupa-like inactive stage) consists of a complicated metamorphosis. 



Almost all Arachnida live on animals, a few on vegetable juices. 

 The lowest forms are parasitic. The larger and moi-e highly orga- 

 nised forms prey on living animals, principally on Insects and Spiders, 

 and are usually furnished with poison weapons, with which they kill 

 their prey. Many of them, by means of the secretion of spinning- 

 glands, spin webs, in which their prey becomes entangled. Most of 

 them remain during the daytime beneath stones and in hiding-places, 

 and come out to catch their prey only in the evening and at night. 



Order 1. LINGUATULIDA,* PENTASTOMIDA. 



Parasitic Arachnida with ringed, elongated, vermiform body, with 

 two pairs of hooks in the neighbourJtood of the jaivless mouth. 



The vermiform ringed body of these parasites, which were for a 

 long time taken for intestinal worms, is to be regarded as being 

 principally formed of the extremely enlarged and elongated abdomen, 

 the cephalo-thorax being much reduced ; an interpretation which the 

 form, of the body of the Dermatophili seems to support. In the 

 adult, jaws are completely wanting, but there are four curved hooks 

 (two on each side of the mouth, tig. 377), which can be protruded 

 from pouches in the skin and are attached to special chitinous rods. 

 These may correspond to the terminal claws of the two posterior 

 pairs of legs, since the two pairs of legs of the larva, which are to 



* E. Lcuckart, "Ban und Entwickelungsgescbichte cler Pentastomidcn," 

 Leipzig und Heidelberg, 1860. 



