120 Development of the Electric Organ of Raia batis. [Apr. 26. 



April 26, 1888. 



Professor Gr. G. STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " On the Coagulation of the Blood." Preliminary Communi- 



cation. By W. D. Halliburton, M.D., B.Sc, Assistant 

 Professor of Physiology, University College, London. 

 Communicated by Professor E. A. Schafer, F.R.S. (From 

 the Physiological Laboratory, University College, London.) 

 Received March 20, 1888. 



[Publication deferred.] 



II. " On the Development of the Electric Organ of Raia batis." 



By J. C. Ewart, M.D., Regius Professor of Natural History, 

 University of Edinburgh. Communicated by J. BURDON 

 (Sanderson, F.R.S. Received March 21, 1888. 



(Abstract.) 



The paper consists of a short description of the electric organs 

 found in the skate genns, and of an account of the development of 

 the electric organ of the common grey skate (Raia batis). 



It is shown that while in some skates (e.g., Raia batis and others) 

 the organ is made up of disk-shaped bodies, in others (e.g., Raia 

 fullonica)it consists of numerous cup-shaped structures provided with 

 long or short stems. 



The disks (with the development of which the paper chiefly deals) 

 consist essentially of three layers, viz., (1) an electric plate in front in 

 which the nerves end ; (2) a striated layer which supports the electric 

 plate ; and (3) an alveolar layer, posterior to which is a thick cushion 

 of gelatinous tissue. Each disk is formed in connexion with a muscular 

 fibre. In young embryos there is no indication of an electric organ, 

 but in an embryo 6 or 7 cm. in length, some of the muscular fibres at 

 each side of the notochord are found in process of conversion into 

 long slender clubr having their heads nearest the root of the tail. 



The club- stage having been reached, the muscular fibre next 



