ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 515 



largely independent of activity ; these advantages have bsen gained by 

 a greater expenditure of energy. 



Variation in Echidna.* — Dr. E. Broom comments on the frequency 

 of variability in regard to the dorsal-lumbar, sacral, and caudal vertebra? 

 in Echidna, and describes a case in which there were eight cervical 

 vertebrae. The eighth, which should have been the first dorsal, closely 

 resembles the normal first dorsal save for its rudimentary ribs. The 

 first dorsal bears ribs which articulate with the sternum in the position 

 normally occupied by the second rib. 



Evolution of the Auditory Ossicles.f — Dr. H. Gadow maintains the 

 validity of the conception which he has previously expressed as to the 

 homologies of the ossicles of the ear and neighbouring parts. He holds 

 that the chain of bones and cartilages between the auditory capsule and 

 the proximal part of the mandible is homologous wherever such a chain 

 occurs ; that this chain in its entirety is homologous with the whole 

 hyomandibula of Elasmobranchs ; that in the Tetrapoda this chain, in 

 conformity with, and in adajitation to, or perhaps caused by, the flattened- 

 down and broadened-out configuration of the suspensorial region of the 

 skull, has been bent at an angle, the apex of which abuts against the 

 tympanic membrane. The part of the chain between tympanum and 

 auditory caj>sule has acted as a conductor of sound, ever since it was 

 relieved of its primary suspensorial function. It is immaterial from a 

 general point of view whether this chain consists of only two pieces 

 (columella and extracolumella in Sauropsida), or forms three- or four- 

 jointed pieces, as in Anura and Mammalia. The extracolumella is homo- 

 logous with the malleus and incus. The string of connective-tissue, often 

 cartilaginous, from the processus internus of the extracolumella to the 

 articular, is homologised with the cartilaginous continuation of Meckel's 

 cartilage into the malleus of foetal and young mammals, and may be 

 compared to the hyomandibular-mandibular ligament of hyostylic Elas- 

 mobranchs. Dr. Gadow's interesting paper, of which this report gives 

 only a hint, is accompanied by some lucid figures, including one of the 

 " terrible intermediate stage " involved on the rival interpretation — a 

 critical stage when the Promammal could not use its jaw and could not 

 hear. 



Otoliths and Hearing.! — Pierre Bonnier refers to Marage's recent 

 argument that the dense labyrinth-fluid forms an excellent conductor 

 for sound, and that the otoliths serve to maintain this acoustic con- 

 ductibility. For ten years Bonnier has sought to show that neither the 

 otoliths nor the " acoustic conductibility " have anything to do with 

 hearing. In man, for instance, the calcareous masses are found in the 

 utriculus and sacculus which are not auditory, and are absent iu the 

 cochlea ; otoliths are most developed in Invertebrates and Fishes, which 

 do not hear ; from Amphibians onwards there is a diminution in the 

 importance of the otoliths and a simultaneous development of hearing ; 

 in the development of Vertebrates the labyrinth-fluid is very rich in 



* Proc. Liun. Soc. N. S. Wales, xxv. (1900) pp. 733-4 (1 fig.). 



t Anat. Anzeig., xix. (1900; pp. 396-411 (6 tigs.)- 



% Compter Rendus, exxxii. (1901) pp. 1367-9. Cf. this Journal, ante, p. 403. 



