248 ENTOMOLOGISK TIDSKRIFT IQ I 7. 



cylindrical externally, and more or less projecting, with a 

 lar<j;e external opening, but funnel-shaped and twisted 

 vviihin»; each has an organ projecting from it, viz. a hair, 

 which varies in shape, being clavate or broadly flabellate, 

 etc., most frequently having a long and thin stalk and the 

 terminal part expanded, while sometimes the organ is nearly 

 globular with a very short stalk. The organs are placed 

 dorsally on the body rather far in front and more or less 

 near the lateral margins. MICHAEL said that »it seems most 

 natural to suppose hearing or smell (I incline the former) to 

 be resident in these organs», but I am more inclined to 

 compare them with the organs substituting the eyes in the 

 Palpigradi. — On other sensory hairs in Oribatidae Michael 

 says: »At the distal end of the tibia of the first leg there is 

 almost always a very long setiform hair arising from the 

 upper median line ... it evidently has a tactile office, and 

 I call it the tactile hair. A similar hair, smaller in size, is 

 frequently found on the tibia of the second leg, and some- 

 times on those of the two hinder pairs». - — According to 

 Michael (1901) theTyroglyphidae have a tactile hair on the 

 tibia of the two anterior, frequently also on the two posterior 

 pairs of legs. — In Trombiduim f7iligiiios7un Henking (1882) 

 found a very complex sensory organ placed dorsally and 

 far in front in the median Ime of the body; what he says 

 on »Tastborsten» on the legs is very explicit, but the setae 

 mentioned are uncommonly simple. 



C. Other external sensory Organs. 



It may be justifiable to enumerate here the other kinds 

 of sensory organs hitherto observed in Arachnids. The only 

 feature they have in common is that no hair is observed. 



Let us begin with the so-called lyriform organs. Seen 

 by transmitted light they seem to be fissures in the chitine 

 with a very or extremely small round dilatation at the 

 middle or towards one of the ends of each fissure. The 

 fissures are either single and scattered or collected in groups; 

 in these the fissures are either rather irregularly distri- 

 buted or so regularl}^ shaped and arranged that the name 



