198 . F. G. HEATHCO'ra. 



elusion ttat the two structures present a very great morpho- 

 logical resemblance. If his arguments hold good it seems to 

 me permissible to compare the hairs of Scutigera to those in 

 the auditory sac in Crustacea, and also to the auditory rods 

 (Horstifte) in insects. 



There is one point, however, in which the organ of Scutigera 

 differs greatly from the tympanic organ, viz. in the absence 6f 

 a tracheal vesicle. I think it doubtful, howevet, whether this 

 tracheal vesicle is an essential part of the insect auditory 

 organ. The swelling of the tracheal trunk seems not to take 

 place in all cases (Leydig, 1. c), and Hensen, in giving 

 ■what he considers the most probable hypothesis as to the 

 action of the tympanic organ, says : "Die tracheen schwin- 

 •gungen sind ohne Bedeutung.' Balfour, in his short account 

 of the auditory organ of terrestrial insects (' Comp. Emb.,' ii, 

 433), does not mention the tracheal vesicle. 

 - I have exarnined this sense organ of Scutigera, both by dis- 

 section and by means of sections. I found that the tissues 

 were best preserved by a mixture of corrosive sublimate and 

 acetic acid. The difficulty of cutting the chitin in sectioning 

 •was overcome by embedding in very hard paraffin. 



My investigations were entirely carried on in the Cambridge 

 Morphological Laboratory .^ 



■ 1 Since forwarding this paper (November, 1884) to the editor of this 

 Journal my attention has been drawn to a paper by Dr. Haase in Schneider's 

 ,' Zool. Beitrage,' 1884, upoii " Schlundgerust uad Maxillarorgan von 

 Scutigera." 



As I am on the point of leaving England on a long voyage it is now too 

 late for me to make an extensive reference to this work, but I may add that 

 in my opinion Dr. Haase's observations do not necessitate any alterations in 

 the foregoing paper. 



