NOTES AND OBSERVATIONS ON BOARD H.M.S. RATTLESNAKE 8S 



The perfect spermatozoa have long, pointed, somewhat triangular 

 heads about aij-Viith of an inch in 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. [Plate lo] 



Fig. 4. Section of Tcthya ; natural size : a, corticle substance ; b, intermediate substance ; 

 1', central substance ; d, canals. 



Fig. 5. Portion of central substance (a) with two of the radii [b]. 



Fig. 6. Segment of the cortical and intermediate substances ; a, cortical substance ; b, inter- 

 mediate substance ; c, canals cut across ; d, radii. 



Fig. 7. A portion of the cortical substance : tz, inner fibrous portion ; /?, radial bundle of 

 rods ; c, stellate bodies ; d, marginal homogeneous portion. 



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

 spermatozoa and cells ; f, 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 indebted 

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

 the correctness of any of the determinations of the auditory organ in 

 Crustacea hitherto given. They describe a very singular organ exist- 

 ing in the caudal appendages of Mysis flexuosa, consisting of an oval 

 flattened sac or cavity Jrd of a line in diameter, and containing an 

 otolithe 5-^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 nerve was traced to this sac, but the caudal ganglion is of 

 large size. 



No similar organ exists in Palmmon, Crangon, or Squilla, but the 

 authors compare it to the organ noticed by Souleyet in Lucifer ; and 

 notwithstanding the extraordinary position of the organ, it must be 

 allowed that its structure goes far to support this view. It must be 

 remembered that in some of the lower Annelida the auditory organs 

 are situated, not in the head,' but one or two rings behind it, and in 

 Polyophthalmus every ring has its pair of eyes. — See Quatrefao-es 

 Ann. d. Sc. Nat. 1850. 



' Beitiiige zur Kenntniss Wirbelloser Thiere. 



