16 ARKIV FÖR ZOOLOGI. BAND 2. N:0 8. 



Organs of Respiratioii. — In the description of the re- 

 spiratory organs in Ricinulei ^ we pointed out the two diffe- 

 rent types of such organs which, according to our opinion, 

 are found in Arachnida. We showed that — apart from 

 the order of Acari which in many respects exhibits much 

 variety — in the same order or in closely alHed orders of 

 Arachnida only one of these two types is met with. In the 

 Pedipalpi only »iungs» — a not very appropriate denomina- 

 tion — are found; such »lungs», which are a variety of one 

 of the types mentioned, consist of a generally sac-shaped 

 tracheal trunk from the bottom of which a very large num- 

 ber of closely arranged, very oblong, strongly compressed, 

 ]amellar »pouches» originate; the short axis of these lamellae 

 is not fully vertical, while their long axis is directed horizon- 

 tally forwards. But as these »lungs» show some not uninter- 

 esting difference in the Pedipalpi we shall give a brief de- 

 scription of the somewhat varying manner in which »lungs» 

 appear in Arachnida. 



In Scorpiones the spirades of the four pairs of lungs are 

 — as is known — found in the sternites of the segments in 

 question, either near the middle or considerably more behind, 

 often twice as far from the anterior as from the posterior 

 margin of the sternite and at some distance from its lateral 

 margin. In most genera the spirades are shaped as träns verse 

 but more or less oblique, posteriorly feebly concave slits, the 

 inner end of which lies more in front than the outer one. 

 The spirade is bounded by a distinct, a little raised, less or 

 more chitinized ring. The »lungs» themselves we have in- 

 vestigated in Buthus europcEtis. The trunk is shaped as a sac 

 which expands somewhat inwards and more outwards across 

 the longitudinal axis of the animal ; it is considerably shorter 

 {less deep) than the length of the spirade. The sac, seen 

 on a longitudinal vertical section of the animal, is shaped 

 nearly as a flat triangle, the posterior side of which proceeds 

 upwards and much backwards, the lower side is somewhat 

 shorter and proceeds horizontally forwards, while the third 

 side, the bottom of the sac, is much longer than any of the 

 two others and slopes from above downwards and much for- 



^ H. J. Hansen and W. Sörensen: On two Ordois of Arachnida: 

 Opiliones, espeeially the suborder Cyphophthahiii, and Ricinulei. namely 

 the family Cryptostemmatoidse. 4*^, Cambridge, 1904. 



