1911.] NATURAL SCIENCES OF PHILADELPHIA. 375 



THE LYRIFORM ORGANS AND TACTILE HAIRS OF ARANEADS. 



BY NORMAN EUGENE M'lNDOO. 



Introduction and Methods 375 



A. The Lyriform Organs 376 



I. Morphology 376 



1. Structure 376 



2. Disposition 380 



(a) Theridium tepidariorum Koch 380 



(6) Other Species 385 



(c) Individual and Sexual Variations 395 



(d) Conclusions 396 



3. Discussion 398 



(a) Disposition 398 



(b) Structure , 399 



(c) Disposition in Other Orders of Arachnids 400 



(d) Phylogeny 401 



II. Physiology 402 



4. Experiments 402 



(a) Olfactory Sense 402 



(b) Hearing* 405 



(c) Function of the Lyriform Organs 406 



(1) Temperature Sense 409 



5. Discussion 410 



(a) Function of the Lyriform Organs 410 



(b) Olfactory Experiments 410 



(c) Sense of Hearing 411 



B. The Tactile LIairs 413 



Bibliography 415 



Explanation of Plates XXX-XXXIII. 416 



Introduction and Methods. 



Since the discovery of the lyriform organs in 1878 only two impor- 

 tant papers have appeared in regard to them. The object of this 

 present paper has been to make an accurate and careful study of their 

 morphology and physiology. The tactile hairs were later taken up 

 in connection with the lyriform organs because their innervation 

 was very similar to that of the latter structures. 



The work has been prosecuted under the direction of Professor 

 Montgomery, to whom I am indebted not only for the majority of my 

 specimens, but also for suggestions and kindly criticisms which have 

 made this work possible. He suggested this subject because these 

 organs are so little known. The exotic species were kindly sent by 

 Dr. Purcell, of South Africa; by Dr. Petrunkevitch, of Yale University, 

 and by Mr. Nathan Banks, of the U. S. National Museum. The 



