48 



NOTES AND MEMORANDA. 



lining of the sac, closed anteriorly, but merely constricted behind. 

 Similarly the third and fourth pairs of bodies, which are in close 

 contact with one another, are connected to the front wall of another sac, 

 the anterior closed end of which fits into the neck of the former, while 

 its own neck extends nearly to the apex of the main sac. Probably 

 these capsules are outpushings of the chitinous lining of the main sac. 

 It will be seen that there are thus formed three capsules, the 

 actual lining of the sac and the two " Binnensiicke," which enclose 

 one another like the coats of an onion, so that while the first pair of 

 stalked bodies has only one layer of chitinfe outside it, the second pair 

 has two, and the third and fourth pairs three. 



The author, " proceeding by the process of elimination," points out 

 that the organ must be either a gland or a sense-organ, and after 

 going over the arguments for and against, comes to the conclusion 

 that it cannot be a gland ; and, further, that partly from its position 

 and partly from its structure it cannot be intended for touch, smell, 

 taste, or vision, and must therefore be a true auditory sac. The 

 stalked bodies he considers to be otoliths, acting from their mode 

 of attachment like the clapper of a bell. 



Plate IV. Fig. 2. — The dipterous larva — natural size — showing 



the position (x) of the supposed auditory organ. 

 Fig. 2 a. — The organ, isolated. K, Fundus of the sac ; Sp, its apex; 

 ep, Ke, its epithelium ; Ca, Chitinous sac ; s^, s^, S3, its three 

 internal capsules (" Binnensacke") ; e, constriction in the neck 

 of the second of these ; st, Stalked bodies ; m, Muscles ; lij, n^, 

 First and second nerves ; ga, Ganglionic swelling on the first 

 of these ; n, branch of the second ; r, Tubular prolongation of 

 the sac. Amj)lification ^^ Zeiss Immers. L. 

 At the end of his paper Graber gives the following useful 

 diagram, showing in a tabular form the various forms of auditory 

 organs occurring in the animal kingdom. 



Chief Forms of Auditory Organ. 



Elementary Auditonj Organ. 



Isolated auditory cells and 



auditory hairs. 



Lower animals (?). 



Crustacea. 



Insects (?). 



Sac-like Auditory Organ, 

 or Cystic Form. 



Tympanic Form (with 

 auditory rods). 



Orthoptera. 



Wall consisting of cells only. 



Gymnotocysts. 



Wall with a chitinous cuticle. 



Chitinotocysts. 



With ciliated cells. 



Ciliotocysts. 



A- 1 



Mono- >lithophorous. 

 Poly- ) 



Ccelenterata (?). 

 Vermes. 

 Mollusca. 

 Vertebrata. 



Cells without cilia. 



Non- ciliated 



gymnotocysts. 



rolylithoiDhorous, 



Ptychoptera. 



With rosette-like 



central organ. 



Larva of Corethra 



and 



ChironomusC?). 



With hairs. 



Piliotocynts. 



A- 1 



Mono- >litliophorous. 

 Poly- J 



Crustacea. 

 Insecta 



(antennary 

 otocysts). 



Without hairs. 



Apilose 

 chitinotocysts. 



With stalked 

 otoliths (?). 



riy larva. 



