[Annals N. Y. Acad. Sci., Vol. XII, No. 5, pp. 103 to 118, July 7, 1899.} 



DEVELOPMENT OF THE OSSICULA AUDITA IN 

 THE OPOSSUM. 



Richard Weil. 



(Read November 19, 1898.) 



[Plates II and III.] 



The following is a preliminary report on the development of 

 the ear-bones in the Trinidad Opossum. Owing to a lack of the 

 proper stages of the anatomical material, the present notice will 

 deal only with the development of the malleus and incus. 



Up to the present time, November, 1898, only the higher 

 Mammalia have been investigated with regard to the development 

 of these bones. Meckel, in 1820, first described the embryolog- 

 ical continuity of the malleus with the first visceral, or mandibu- 

 lar, arch, and this statement has since that date never been over- 

 thrown. The question remains : does the incus arise from the 

 first arch, or from the second, or independently ? 



The history of the evidence is briefly as follows : Valentin 

 and Rathke (1835) were the first to maintain the origin of the 

 incus from the first arch, that is to say, its embryonic continuity 

 with the malleus. This view was firmly established in 1838 by 

 Reichert, whose conclusions were verified and amplified by 

 Huxley (1858). In 1869, however, Professor Huxley was in- 

 duced, by his discovery of a direct union by means of cartilage 

 of the stylo-hyal with the columella in Splienodon, to believe 

 that the embryonic appearances had been misinterpreted by 

 Reichert, and that the incus was actually a derivative of the 

 hyoidean arch. This view was taken up by Parker, and re- 

 ceived full confirmation from his embryological researches 

 (1874, 1877), and other and later researches by English investi- 

 gators, noticeably Eraser, have successively accumulated the 



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