Note on the Auditory Organ in Crustacea. 373 



inatozoa in every stage of development from those cells. The cell 

 throws out a long filament which becomes the tail of the sper- 

 matozoon, and becoming longer and pointed forms, itself, the 

 head. 



The perfect spermatozoa have long, pointed, somewhat trian- 

 gular heads about ^ouo*^ ^^ ^^ ™*^^ ™ diameter, with truncated 

 bases, from which a very long filiform tail proceeds. 



It is remarkable that the ova are in no way separated from the 

 spermatozoa, but lie imbedded in the spermatic mass like eggs 

 packed in sand. 



EXPLANATION OF PLATE XIV. 



Fig. 4. Section of Tethya; natural size : a, cortical substance; b, interme- 

 diate substance ; c, central substance ; d, canals. 



Fig. 5. Portion of central substance (a) with two of the radii (6). 



Fig. 6. Segment of the cortical and intermediate substances : a, cortical 

 substance ; b, intermediate substance ; c, canals cut across ; 

 d, radii. 



Fig. 7. A poi-tion of the cortical substance : a, inner fibrous portion; b, ra- 

 dial bundle of rods ; c, stellate bodies ; d, marginal homogeneous 

 portion. 



Fig. 8. A portion of the intermediate substance : a, ova ; b, granular sub- 

 stance consisting of spermatozoa and cells ; c, stellate bodies. 



Fig. 9. Spermatozoa in various stages of development. 



Fig. 10. Longitudinal and transverse view of rods, showing the central 

 canal, a. 



Note — " Upon the Auditory Organ in Crustacea." 



MM. Frey and Leuckart * (for access to whose work I am in- 

 debted to Prof. E. Forbes since writing on this subject) express a 

 doubt as to the con'ectness of any of the determinations of the 

 auditory organ in Crustacea hitherto given. They describe a very 

 singular organ existing in the caudal appendages of Mysis flex- 

 uosa, consisting of an oval flattened sac or cavity ird of a line in 

 diameter, and containing an otolithe ^—g^th of a line in diameter. 

 The otolithe is discoidal, flat on the one side, umbilicated on the 

 other, and marked with concentric lines. About two-thirds of 

 the circumference of the otolithe are occupied by the bases of a 

 series of glassy, stiff hairs which are inserted into the otolithe and 

 project from it. 



The otolithe is apparently composed of chitine and carbonate 

 of lime. 



No nei-ve was traced to this sac, but the caudal ganglion is of 

 large size. 



No similar organ exists in Palamon, Crangon, or Sqidlla, but 

 the authors compare it to the organ noticed by Souleyet in Lu- 



* Beitrage ziar Kcnntniss Wirbclloser Thiere. 



