G. H. F. Nuttall, W. F. Cooper and L. E. Robinson 241 
material are forthcoming, we are unable to complete our work on the 
histology of the soft parts. From the few observations which it has been 
possible to make, it appears that the hypodermal cells immediately 
beneath the sensory hairs are large and flask-shaped; each consists of a 
sac of finely granular cytoplasm surrounding a large central cavity or 
vacuole which communicates directly with the hollow interior of the 
hair. We have succeeded in identifying nerve fibrils running towards 
the bases of the sensory hairs, but cannot, at present, define their 
relationships with the modified hypodermal cells. 
Closely associated with the vesicle of Haller’s organ and included in 
Haller’s description as an intrinsic part, is a pit-like depression which 
we have termed the accessory pit (Plate XVIII, Fig. 1): it lies a little 
distance beyond the distal side of the main vesicle, is widely open to the 
exterior, and is furnished on its floor with a number of short stiff hairs, 
some of which protrude beyond the mouth of the pit. This structure 
appears to have been considered as a small counterpart of the chief 
vesicle, but its appearance, together with the fact that the hairs which 
it contains are quite different in character from those of the latter, does 
not support this view. The surface of the leg on both the proximal and 
distal sides of Haller’s organ bears a cluster of stiff hairs, the function of 
which is, presumably, protective (Text fig. 1). 
As already stated, Haller alluded to the presence of an otolith in the 
cavity of the organ and a repi’esentation of such a body is clearly shown 
in his figure: we have diligently searched for such bodies in all our pre¬ 
parations but have failed to detect their presence and have no hesitation 
in denying their existence. 
In conclusion, we are compelled to doubt that the function of Haller’s 
organ is auditory. Haller based his interpretation on the presence 
of a supposed tympanic membrane, of otoliths, and the resemblance to 
the auditory organs of certain Crustacea. No one, as far as we know, 
has attempted any experimental proof of an auditory function. On the 
other hand, the structure of the organ, the peculiar antenna-like move¬ 
ments of the first pair of legs, and the results of Lahille’s experiments 
are all strongly in favour of the assumption that Haller’s organ is 
olfactory in function. 
