27 



Next to this in extent and value may be ranked Prof. 

 Wyman's paper on the development of the common skate of 

 our waters (Raia JBatis), communicated to the American 

 Academy in 1864, and published among its Memoirs. It 

 gives an account of the peculiar egg-case of the Selachians, 

 and of the several stages of the development of the embryo 

 skate, expressed in the concise and clear language — as little 

 technical as possible, — for which he was distinguished, and 

 leading up to not a few problems in comparative anatomy, 

 morphology, or systematic zoology, — problems which Prof. 

 Wyman never evaded when they came directly in his way, 

 and seldom handled without making some real contribution 

 to their elucidation. For instance, in describing the external 

 branchial fringes of the young skate, he notes the agreement 

 in this character with the Batrachians; and in studying the 

 seven branchial fissures of the embryo, he is brought into 

 contact with the view of Huxley, that the formation of the 

 external ear is by involution of the integument. After con- 

 firming the contrary observations of Reichert, on the embryo 

 pig, he concludes that " the first of the seven branchial fis- 

 sures of the embryo skate is converted into the spiracle, 

 which is the homologue of the Eustachian tube and the outer 

 ear-canal." After a full discussion of the homology of the 

 upper jaw in sharks and skates, under the light afforded by 

 his investigation of the embryo skate, he suggests that the 

 cartilage which extends from the olfactory fossae towards the 

 pectoral fin is the probable homologue of a maxillary bone, 

 and that in the lobe, the homologue of an intermaxillary ; 

 that, if so, the skates and proteiform reptiles agree in having 

 the nostrils open in front of the dental arch ; that while in 

 all Batrachians the nasal groove becomes closed, in the skate 



