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have investigated at all completely the homologies and connections of the 

 plate of cartilage upon whose inferior or palatal face the dumb-bell shaped 

 bone is grafted. Symington, indeed (loc. cit.) accurately describes and 

 figures this cartilage plate in the region of and behind the dumb-bell shaped 

 bone. But he is silent in respect of its anterior relations. Where he de- 

 scribes it, the plate is formed by the alinasal cartilages which are continuous 

 dorsally with the dorsal margin of the septum nasi, but after bending round 

 laterally to form the side walls of the nasal fossae, they turn inwards ven- 

 trally to form its floor and meet but do not fuse in the middle line of the 

 palate. It is here close to their mesio-ventral edges that they are excavated 

 by the cavities of Jacobson's organs, and that they have grafted on their 

 inferior or palatine surfaces the single mesial dumb-bell bone. If, however, 

 these cartilages be traced forwards in a series of sections in front of Jacob- 

 son" s organs and in front of the dumb-bell bone, their mesio-ventral edges 

 are gradually found to diverge from each other so as to admit of the inferior 

 edge of the cartilaginous septum nasi, which descends between them, ex- 

 panding at the same time so as to assume a considerable share in the forma- 

 tion of the cartilaginous palate between the aforesaid alinasals. Still further 

 forwards the lateral margins of this now flattened and expanded septal car- 

 tilage fuse with the now widely separated margins of the alinasals, and the 

 cartilage with this compound origin may be traced forwards right to the 

 anterior end of the snout and into direct continuity with the marginal lip 

 cartilage. Where the lower margin of the cartilaginovis septum nasi descends 

 and expands between the alinasals , it becomes gradually separated off from 

 the upper margin of the septum, so that for an appreciable distance we have 

 two cartilaginous septal elements, one dorsal and the other ventral or pala- 

 tine, joined by an intervening connective tissue portion. But the dorsal 

 portion stops abruptly immediately behind the anterior nostrils , which are 

 dorsal in position. Almost immediately, however, in front of its point of 

 cessation an entirely new cartilage appears, having a peculiar form. It con- 

 sists of a flat ventral plate from whose lateral margins two vertical plates 

 project dorsally, the whole arrangement being placed between the nostrils. 

 This arrangement is continued forwards for a short distance, but is soon 

 much modified by the abrupt disappearance of the lateral plates. The ven- 

 tral plate remains, however, lying parallel to and a short distance dorsal of 

 the palatine prenasal prolongation of the septum, which has already been 

 described. And still further forwards the ventral plate descends still more 

 so as to lie almost in contact with the dorsal surface of the prenasal cartila- 

 ginous plate , and gradually fades away with it , coming into actual contact 

 with it or fusing with it. It is well known that in the pig embryo there is 

 a very large prenasal tract of cartilage , which is the continuation forwards 

 of the axial skeleton of the cranium in that animal. That, however, becomes 

 proportionately greatly reduced in development. But in Ornithorhynchus we 

 must regard such a prenasal expansion of the cranial basis as not only per- 

 manent in adult life, but as attaining in that animal a high degree of struc- 

 tural development and actually taking on a functional importance as part of 

 the skeleton of the muzzle. — 5) On the peculiar rod- like tactile organs in 

 the integument and mucous membrane of the muzzle of Ornithorhynchus. 

 By J. T. Wilson, M.B., Professor of Anatomy in the University of Sydney, 

 and C. J. Martin, M.B.. B.Sc, Demonstrator of Physiology in the Univer- 



