284 ANATOMY OF VERTEBRATES. 



external membrane closing the tympanum : but they are super- 

 added developments to the true serial homologue of the tympanic 

 membrane, shown in Reptilia, vol. i. p. 338, 339, fig. 220 ; and 

 which disappears or blends with the later added developments of 

 integument with special cartilages, muscles, and glandules, and 

 which truly parallel the c pinna ' of the ear. In the eyelids, the 

 meibomian follicles repeat the ceruminous ones, and the eyelashes, 

 the cilia which guard the entry to the meatus auditorius. Wharton 

 Jones compares the muscles of the eyeball to those of the otosteals, 

 and I concur, with him, in accepting the opinion of Weber as to 

 the special relation of both to their respective Organs of Sense, 

 and as to their being parts superadded to the elements of the ver- 

 tebral skeleton. But I believe that the divergence of functions 

 so governs the development of special motive organs and ossicles 

 as to remove the ground for safely or usefully homologising such 

 parts, and I refrain from going beyond the serial repetitions in the 

 eye and ear which are above indicated. 



