JEFFRIES WYMAN. 391 



skull, and supports the opinion that they also are only three 

 in a characteristic manner. 1 



Of this whole memoir it is thought that, notwithstanding 

 the great advance which has been made in comparative ana- 

 tomy during the twenty-live years which have elapsed since 

 it was published, its importance to the student has not at all 

 diminished. 



Next to this in extent and value may be ranked Professor 

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

 our waters (Raia Batis), communicated to the American 

 Academy in 1804, 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 Pro- 

 fessor Wyman never evaded when they came directly in his 

 way, and seldom handled without making some real contri- 

 bution to their elucidation. For instance, in describing the 

 external branchial fringes of the young skate, he notes the 

 agreement of this character in the Batrachians ; and in 

 studying the seven branchial fissures of the embryo, he is 



1 " The conclusions which have been drawn from the statements made 

 above are as follows : that in frogs the vagus comprises the glosso-pharyn- 

 geal and accessory nerves ; that the trigeminus comprises the facial, the 

 ahducens and in the salamanders the patheticus and portions of the motor 

 communis ; that other evidence sustains the hypothesis, that the whole of 

 the motor communis is a dependence of the trigeminus ; if to these we 

 add the hypoglossus (which in frogs is exceptionally a spinal nerve), we 

 shall have three pairs of cranial nerves, each having all the characters <>t 

 a common spinal nerve, namely, motor and sensitive roots and a ganglion ; 

 that there are no nerves to indicate a fourth vertebra, unless the Bpecial 

 sense nerves are considered ; if these are admitted as indica t ions, then ire 

 must presuppose either two pairs of nerves to each vertebra, or the exist- 

 ence of six vertebra, which is a larger number than can be accounted for 

 on an osteologieal basis. The functions and mode of development <>f the 

 special sense nerves we have taken as affording sufficient grounds for 

 considering them as of a peculiar order, and not t<> be classified with com- 

 mon spinal nerves." 



