496 



AEACHNIDA. 



the Mites and Spiders amongst the Arachnida, although they possess 

 a greater number of appendages than either, inasmuch as the males 

 have an accessory pair of legs, used in carrying the eggs (fig. 389, A 

 B}. They are small animals with a conical suctorial proboscis and 

 rudimentary abdomen (reduced to a tubercle) ; and they live in the 

 sea, and crawl slowly about amongst the sea-weeds. There are four 

 pairs of very long, many-jointed legs, which contain tubular cliver- 

 ticula of the stomach and the sexual glands. There are no tracheae. 

 On the other hand, there is a well-developed heart with an aorta 



FIG. 300. Ammothea pygnogunoides (regne animal). Da, prolongations of alimentary 



canal into the legs. 



and several lateral ostia. Above the brain lie four small simple 

 eyes. There is a considerable ventral chain, composed of several 

 ganglia. The eggs are carried about on the accessory pair of legs on 

 the thorax of the male (fig. 389) till the larvae are hatched. 



Pygnogonum littoral < 0. Fr. MUller, North Sea. Pho-ri chili (Hum Edw., 

 Awimothc-a Leach, A. pygnogonoides Quatr. (fig. 390). 



TARDIGRADA.* 



The Tardigrada constitute a second group, which is often separated 

 as a distinct order. They are small mite-like Arachnida, and may 



* Doyere, " Mdmoire sur les Tardigrades."' Ann. tffx XT-. ICttt., IP Ser., Tom. 

 XIV., XVII.. XVIII. C. A. S. Schultze, " Macrobiotus Hnfelandii, etc," Berolini, 

 1834. C. A. S. Schultze, " Echiniscus Bellermanni, " Berolini, 18-iU. Dnjardin, 



