1887.] On the Blood-Vessels o/Mustelus Antarcticus. 437 



■electrodes were measured by means of a high resistance reflecting 

 galvanometer, suitably arranged, with shunt and interposed resistance, 

 for the purpose in hand. 



The result of my experiments is to bear out completely the deduc- 

 tion which I had made from Mr. Mortimer Evans' numbers ; and to 

 show that the temperature which produces, for example, the appear- 

 ance of a certain red heat, is very much higher when the surface of 

 the heated body is dulled than when it is bright as in a polished 

 metal. I am not yet prepared to give a definite numerical com- 

 parison ; but in order to show that the difference of temperatures 

 referred to amounts to many degrees of temperature, I may be 

 allowed to give the following statement. 



The two wires being at the same dull red heat, which from previous 

 experience I estimate at perhaps 600° C, in the case of the bright- 

 surfaced wire, the ratio of the resistance of the lamp-blacked platinum 

 to the bright platinum was 130 : 93. Platinums differ very much as 

 to variation of resistance with temperature ; but in most specimens 

 the resistance is doubled, when the temperature is raised from 0° C. 

 to a temperature of from 300° C. to 400° C. ; and for any particular 

 platinum wire the change in resistance is almost in simple proportion 

 to the change in temperature. From this statement it may be judged 

 that the difference of temperatures between the two platinums, dull 

 and bright, when giving out the same light, was a great many degrees 

 centigrade. 



The difference of temperatures of the two glass envelopes was also 

 very striking. The glass tube containing the bright wire was not 

 even unpleasantly warm; while in the case of the other it was so hot 

 as to blister the skin of the hand ; and in this connection it is to be 

 remembered that the vacuum in the two tubes was the same. 



I propose as soon as possible to continue this investigation and 

 render it more complete. 



XXIV. " Note to a Paper on the Blood-vessels of Mustelus Antarc- 

 ticus ('Phil. Trans.,' 1886)." By T. Jeffery Parker, B.Sc. 

 Lond., Professor of Biology in the University of Otago. 

 Communicated by Professor M. Foster, Sec. U.S. Received 

 May 2, 1887. 



My attention has been called by a perusal of Professor Milnes 

 Marshall and Mr. C. H. Hurst's 4 Practical Zoology' (London, 1887), 

 to an omission in my description of the venous system. These authors 

 describe and figure, in Scyllium canicula (pp. 218 and 224) a trans- 

 verse anastomosis, the inter-orbital sinus, connecting the right and 



