1898.] voyage to Melanesia during the years 1894 — 1897. 401 



of development are to be found in the uteri of one female, indicate 

 a very striking correspondence with the Neotropical species. 



The embryos are provided with a large ectodermic trophoblastic 

 organ apparently formed by the dilatation of the primary body- 

 cavity. Of the thirteen specimens only two were males, but the 

 examination of the older embryos taken from the larger females 

 showed that the number of legs in the respective sexes was con- 

 stant. It is probable that the embyros of this species will throw 

 a side-light on the " placental " development of the Neotropical 

 species as described by Kennel. 



Monday, 21 February, 1898. 

 Mr F. Darwin, President, in the Chair. 



The following communications were made to the Society : 



(1) On some differential equations in the theory of symmetric 

 algebra. By Professor Forsyth. 



This paper is printed in the Transactions, Vol. xvi. Part iv. 



(2) The Discharge of Electrification by Ultra-violet Light. 

 By E. Rutherford, M.A., B.Sc, 1851 Exhibition Scholar New 

 Zealand University, and Coutts Trotter Student, Trinity College, 

 Cambridge. 



The general action of ultra-violet light on the discharge of 

 electrification has been investigated by many different experi- 

 menters. Hertz 1 in 1887 first drew attention to the action of 

 ultra-violet light on a spark gap. Wiedemann and Ebert 2 showed 

 that the kathode was the seat of this action and investigated the 

 general effect on high potential discharges. Hallwachs 3 and 

 Righi 4 observed the fact that zinc and other metals became 

 positively electrified under the action of ultra-violet light. These 

 results were extended by Elster and Geitel 5 , who have published a 

 series of papers on the effect of ultra-violet light in causing 

 discharge under various conditions and have also 6 investigated 



1 Wied. Annal. xxxi. p. 983. 1887. 



2 Wied. Annal. xxxm. p. 241. 1888. 



3 Phil. Mag. xxvi. p. 78. 1888. 



4 Phil. Mag. xxv. p. 314. 1888. 



5 Wied. Annal. xxxviii. p. 40, xxxviii. p. 497, xxxix. p. 332, xli. pp. 162, 166, 

 hi. p. 433, lv. p. 684. 



6 Wied. Annal. xli. p. 166. 1890. 



