1892.] The Electric Organ of the Skate. 475 



completely invested by the last unaltered muscular cone. From the 

 first to the tenth the cones slightly increased in length ; but from 

 the eleventh they diminished in length, the twenty-sixth measuring 

 only 0'75 cm. Beyond the twenty-eighth there were from six to 

 eight incomplete cones. 



In transverse sections the anterior third of the organ was seen to 

 present an oval or rounded form, while the middle and posterior 

 thirds were less regular, owing to the organ coming into contact 

 with the vertebral column, and being grooved by the dorsal and 

 ventral muscles. 



The cones are described as consisting of numerous loculi or 

 chambers, each having an electric disc suspended by nerve fibres 

 from its anterior wall, and occupied in front and behind the disc 

 with gelatinous tissue. 



It is estimated that each organ in R. batis is made up of about 

 10,000 electric elements, i.e., about 20,000 in the two organs. Tor- 

 pedo marmorata has about 500,000, and T. gigantea about 1,000,000, 

 elements in the two batteries, all considerably larger than those of 

 the skate. 



The layers of the electric discs, the electric, striated, and alveolar, 

 are described in detail ; and the various views as to the termination 

 of the nerve fibrils in the disc are referred to. 



In the chapter on the progressive growth of the organ a table is 

 given to show that in B. batis the organ, after a time, grows at a 

 greater rate than the tail in which it is lodged, e.g., in fish 60 cm. in 

 length the tail measures about 28 cm., and the electric organ 

 22'5 cm. ; well-formed discs having an area of 0'8 to 1 sq. mm. 

 In fish 225 cm. in length the tail measures 85 cm., the organ 70 cm., 

 and the discs have an area of about 2'08 sq. mm. In fish from 

 25*5 to 30'5 cm. in length the organ is from 12' 78 to 14'0 cm., and 

 weighs 0'5 to 0'6 gram ; in fish from 83'5 to 91*25 cm. the organ is 

 from 30'50 to 34'25 cm., and weighs from 6'0 to 8'0 grams ; in fish 

 157 cm., the organ measures 48'25 cm., and weighs 25'00 grams; 

 while in 225 cm. fish the organ, which measured 70'00 cm., weighed 

 156'00 grams. These facts, especially the great size and weight of 

 the organ in large skate (about 7 feet in length), do not seem to 

 point to the skate's organ being in process of degeneration; more 

 especially as the increase in size is not accompanied by any histologi- 

 cal changes of a retrogressive nature, the largest organ examined 

 being apparently as perfect as that of Torpedo and Gymnotus. 



In discussing the organ from a physiological point of view, reference 

 is made to the investigations of Sanderson and Gotch, and it is 

 pointed out that, when the electric plate is taken as the unit, the value 

 per square millimetre of the single plate of the skate is in all prob- 

 ability equal to, if not greater than, that of the torpedo. 



