no 



SCIENCE. 



[N. S. Vol. XIV. No. 342. 



scended from those of Sauropsida. The first 

 contention is based upon the embryonic connec- 

 tion of malleus and incus with the Meckelian 

 bar, upon the embryonic situation of the last 

 anterior to the Eustachian tube, and upon the 

 innervation of the muscle of the malleus by a 

 branch of the trigeminus. Embryonically, 

 however, the malleo-incudal complex, in addi- 

 tion to its continuity with the Meckelian bar, 

 arises from the auditory capsule, which con- 

 tributes to both malleus and incus, the stroma 

 of the tympanic cavity, contributing to the 

 manubrium mallei, and a membrane bone which 

 forms the Fallopian process. Furthermore, as 

 Gegenbaur points out, the continuity of mal- 

 leus and incus, if they be the quadrate and 

 articular, is itself in contradiction to the inde- 

 pendent embryonic origin of these elements in 

 the lower forms. The pre-trematic origin of 

 the ossicles in the pig, as described by Kings- 

 ley, is contrasted with their post-trematic, or 

 hyoidean, origin in lower forms. Dr. Weil 

 stated that his studies of a full series of pig and 

 opossum embryos did not enable him to decide 

 whether the malleus, and still more, the incus, 

 lay primarily in front or behind the tube. The 

 bones cross the anlage of the tube in a trans- 

 verse direction, lying above it ; by the gradual 

 absorption of the intervening stroma they come 

 to occupy the cavity of the tympanum. Finally, 

 the innervation of the tensor tympani muscle 

 of the malleus by a branch from the otic gan- 

 glion of the trigeminus is taken to indicate the 

 relation of the malleus to the mandibular arch. 

 But lesions of the trigeminus at its root do not 

 involve hearing, while the contrary is true of 

 lesions of the facial. This fact would point to 

 the origin of the above-mentioned nerve from 

 the seventh nerve, and would make the mal- 

 leus a part of the second arch. The second 

 contention is supported, first by the difference in 

 the embryonic relations of the bones to the Eu- 

 stachian canal, an argument already considered, 

 and second, by the differences in the relations of 

 the chorda tympani nerve, which in Sauropsida 

 crosses above the chain, and in mammalia below 

 it. The speaker showed that the pathologists, 

 from a comparison of a large number of lesions 

 of the trigeminus and of the facial at the base of 

 the brain, had demonstrated the exit of the 



chorda tympani in man with the roots of the 

 former. But siuce it leaves the brain in lower 

 forms with the seventh, its relations to bony 

 structures are evidently not sufficiently constant 

 to constitute a criterion of homologies. From 

 these facts, it would appear that the homology 

 of malleus and incus with the quadrate and 

 articular has not yet been demonstrated. 



Dr. Mayer showed that the snails in question 

 are subjected to conditions of isolation very 

 similar to those affecting the Achatinellidse of 

 Oahu in the Hawaiian Islands, occurring in 

 valleys which are separated by comparatively 

 barren ridges. The farther apart the valleys, 

 the less intimate is the relationship between 

 their snails. Although geographical isolation 

 is probably the chief factor in determining the 

 establishment of definite varieties, yet the dif- 

 fering environmental conditions obtaining in 

 each valley may exert considerable influence. 



Dr. Strong presented a preliminary report, 

 illustrated by lantern slides, upon a case of uni- 

 lateral atrophy of the cerebellum in a child 

 which lived to the age of three years and four 

 months. The principal external anomalies 

 noted were the following : The left hemisphere 

 of the cerebellum was almost entirely absent ; 

 the right olive was wanting and the trans- 

 verse pontile fibers on the left side were de- 

 ficient ; the left half of the pons protruded more 

 than the right ; the right crus cerebri was much 

 narrower than the left ; the left restiform body 

 was smaller than the right, and the superior 

 cerebellar peduncle of the left side was de- 

 ficient ; the posterior corpora quadrigemina 

 were asymmetrical, while the left anterior 

 corpus quadrigeminum was apparently lacking ; 

 the median line of the fourth ventricle was 

 curved with its convexity toward the left, and 

 such structures of the medulla as the clava, 

 cuneus, ala cinerea, and eminentia teres were 

 located or extended further cephalad on the 

 left side than on, the right. Preliminary 

 transverse sections cut at various levels through 

 the medulla, pons, isthmus and posterior 

 corpus quadrigeminum showed the following 

 points : only small parts of the right olive and 

 the left corpus restiforme wei'e present, and 

 there was a corresponding deficiency of the 

 cerebello-olivary fibers ; the transverse pontile 



