258 
F. G. HEATHCOTE. 
elusion that 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 of 
a tracheal vesicle. I think it doubtful, however, 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, 
423), does not mention the tracheal vesicle. 
I have examined 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 
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, upon “ Schlundgerust und 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. 
