TARDIGRADA. 859 



the Myzostomida shows that their position in the animal king- 

 dom is very indeterminate. 



Those Tardigrades which live amongst moss, like some Rotifers 

 and Nematodes, possess remarkable powers of undergoing desic- 

 cation without being injured in any way by the process of drying 

 up. As the moisture diminishes, the little creatures cease to 

 move and begin to shrivel up until they resemble a small grain 

 of sand. After rain or heavy dew, however, they slowly revive, 

 swell up to their former size, and behave as if nothing had 

 interfered with their former activity. 



Fam. 1. Echiniscidae with the characters of the order. 



The following genera are recognized : Echiniscus C. Sch. ( = 

 Eurydium Doy.) a widely distributed genus found in the Arctic 

 region and on mountains up to 11,000 feet and elsewhere. There 

 are numerous species and one sub-genus Echiniscoidesoi which the 

 single species Echiniscoides sigismundi lives amongst sea-weed. 

 Microlyda (Lydelld), one species with elongated legs, is another 

 marine form. Macrobiotus w r ith many species lives amongst 

 moss or in fresh- water. Doyeria with a single species also live& 

 amongst moss. Diphascon with several species occurs in Europe, 

 Spitsbergen and Chili. Milnesium has two species. 



APPENDIX II TO THE ARACHNID A.* 



Order PENTASTOMIDA. 



Elongated, vermiform parasites with ringed bodies, a pair of 

 claws on both sides of the mouth, no respiratory or circulatory 

 organs, larval form present. 



The Pentastomida, with but three genera, Porocephalus, Lingua- 

 tula and Reighardia,-\ are exclusively parasitic and pass the 

 adult stages of their life in the noses and adjacent sinuses of 

 flesh-eating vertebrates. Their eggs when fertilized, are sneezed 

 out or coughed up, and, falling on grass or plants, are eaten by 

 some vegetable-feeding animal. When they reach the stomach, 



* W. Stiles, Zeit8chr.wiss.Zool.,\n, 1891. Lohrmann, Arch. Naturg.,lv,. 

 1889. A. E. Shipley, Arch. Parasit., i, 1898. 

 t H. B. Ward, P. Amer. Ass.. 1899, p. 254. 



