322 NATURAL SGIJ^NCE [May 



position it could only play over some part of the hind-body or 

 abdomen. Now, it is well known that in most spiders the hind- 

 body is soft-skinned. The breathing organs or " lung-books," how- 

 ever, situated one on either side of the front end of the hind-body, 

 are always covered by plates which are somewhat hardened. And 

 microscopical examination soon showed that in the present spider 

 these lung-book covers are completely chitinised, and that their sur- 

 face is provided with a beautiful and complex arrangement of ridges 

 and furrows. With the analogy of the stridulating organs of other 

 spiders before us, there can be no doubt that the purpose of this 

 apparatus is to produce sounds. 



A more highly magnified view of a lung-book cover from the side 

 is shown in fig. 2 ; and it will be seen that in the lower (ventral) 

 region of the plate the ridges are somewhat coarse, and parallel, with 

 numerous finer transverse ridges between them. But in the upper 

 (lateral) region the ridges are all fine, and form an irregular network. 

 It is likely that the note produced is relatively high or low, accord- 

 ing as the fine or coarse ridges are brought into friction with the 

 spine on the basal segment of the leg. Or it is possible that the 

 irregular network may represent the primitive generalised sculpture 

 of the surface of the lung-plate, and that only the parallel series of 

 ridges are concerned in the production of sound. 



Unfortunately, only a single male was obtained, so that it is 

 impossible to say whether this organ is present also in the female. 

 Its function is almost certainly to produce a sexual " call -note " or 

 " love-song," for the apparatus is so minute that the pitch must be 

 too high for the sound to be of use as a " warning- note." Many 

 problems of interest are presented to the student of spiders by these 

 stridulating organs. It is remarkable in how few forms compara- 

 tively they are present ; and these by their structure and distribution 

 are mostly seen to be ancient and decadent groups. How is it that 

 species possessed of such wonderful and complex structures have 

 been, to a great extent, thrust aside in the battle of life by rivals 

 which have no such organs ? Geo. H. Carpenter. 



Science and Art Museum, Dublin. 



