ON TRACHEAN ARACHNIDA. 521 



feet goes on increasing, beginning from the second pair. 

 They are shorter and thicker in chelifer (proper) than in 

 ohisium. 



These arachnida are very small. The most common species, 

 the scorpion araignee of Geoffroy, is found in humid places, 

 under stones and garden flower-pots, in the unfrequented parts of 

 houses, in dust, old books, and herbals. It lives on those little 

 insects called psocus pulsatorius by Fabricius, on small acari, 

 and it even attaches itself to flies. Goetze assures us that he has 

 fed it with small aphides. Linnaeus tells us that it sometimes 

 introduces itself into the skin, and there produces a painful 

 swelling of the size of a pea. He even relates, on the faith of 

 Dr. Bergius, that a peasant, during the night, having had his 

 thigh pierced by one of these arachnida, there formed a pus- 

 tule, of the size of a nut, which occasioned most frightful 

 torment. But these facts require authentication. When this 

 arachnid is pursued, or when it meets in its way some object 

 that it is desirous to avoid, it walks tolerably fast, both for- 

 wards, backwards, and sideways, like the scorpion and the 

 crab. Rcesel has seen the female lay small eggs of a greenish 

 white, and assemble them one beside the other. But he has 

 not told us whether the young took a long time to come forth 

 from these eggs. 



The elder Hermann, according to the testimony of his son, 

 has seen the same animal carrying its eggs, gathered up in a 

 pellet under its belly, after the fashion of many arane'ides. 

 He once found one of them enclosed in a silken follicle, 

 covered with dust, and attached to a wall by one of its sides. 

 It is M. Latreille's opinion that this cocoon was foreign 

 to this animal, and that it merely made it its temporary 

 domicile. 



The Pycnogonides appear to M. Savigny to form the 

 passage from the Crustacea to the arachnida. The Pycno- 

 GONA differ from the other genera of the same family, not 



