632 AKACHNIDA. 



The testes of Ixodes consist of four or five pairs of unequal 

 follicles, opening out near the base of the abdomen." The 

 males are distinguished from the females by their larger "cheli- 

 ceres" (maxillary palpi) and larger pair of clasping legs. In 

 the spiders the testes are "two long, simple, interlaced cseca, 

 concealed beneath the hepatic lobes," which lead bj^ two def- 

 erent canals to the base of the abdomen, through a simple 

 fissure, which, however, is not applied to the vulva. The com- 

 plicated hollow spoon-shaped palpi are supposed to be the in- 

 tromittent organs. '"The}' are filled with sperm and applied to 

 the entrance of the vulva. For this purpose the last joint of 

 the palpi, which is always hollow and much enlarged, contains 

 a soft spiral body, terminated bj' a curved, gutter-like, horny 

 process. Beside this there is an arched, horn}" filament, and 

 several hooks and other appendages of the most varied forms. 

 These appendages are protractile and serve, some to seize the 

 female, and others as conductors of the sperm." (Siebold.) 

 While the majority" of the Araehnida are develope^l as usual 

 after the la^'ing of the eggs, a few, such as the scorpions and 

 Or that idee, and other mites, are known to be viviparous, 

 and it is probable that an alternation of generations occurs in 

 some of the lower mites. The Tardigrades are hermaphro- 

 dites. 



The Araehnida breathe both by trachea and lung-like organs. 

 The mites, the false scorpions, the harvest-men and Solpxi- 

 giclm are provided with tracheae, communicating externally 

 by means of spiracles, generally two in number, and concealed 

 between the anterior feet. In Hj^drachna, which lives con- 

 stantly beneath the water, the tracheae "possess probabl}-, the 

 power to extract from the water, the air necessarj^ for respira- 

 tion." (Siebold.) In the false scbrpions a pair of lateral stig- 

 mata are situated on each of the two basal rings of the 

 abdomen. From these spring "four short, but large trachean 

 trunks from which arise numerous unbranched tracheae spread- 

 ing through the entire body." In the Sol ^lugnlK there are 

 three pairs of stigmata and the trachete ramify and are distrib- 

 buted much as in insects, and in the Phalang idee the tra- 

 cheary system is well developed, arising from two stigmata 

 opening between the insertion of the posterior legs. 



