PROCEEDINGS OF THE SOCIETY. 249 



the required temperature, the cavity which was enclosed between the 

 glass slide and the mica plate would remain constant without further 

 attention. 



Mr. Scourfield exhibited a living specimen of a Copepod, Belisarius 

 viguieri (found in the water collected in the cups formed by the bases 

 of the leaves of Bromeliaceous plants at the Royal Botanic Gardens), 

 to show the peculiar pulsating organ associated with the maxillary 

 gland. When first described (by Maupas) it was thought to be of the 

 same nature as the vibrating organs or " flame-cells " of Rotifers. It 

 was, however, a muscular action, thii apparatus probably acting as a 

 pumping-organ in connexion with the maxillary gland, as had recently 

 been described by Chappuis. So far as he (Mr. Scourfield) was aware, 

 this organ was unique among the Crustacea. There was, however, a 

 pulsating organ in the Cladoceran, Leptodora, shown in his second 

 exhibit, as far as the structure could be demonstrated in a preserved 

 specimen. It occurred at the distal end of the first joint of the first 

 pair of feet, and it was worked by a little cross muscle. The organ 

 was probably useful in connexion with the circulation. Gerschler 

 (1910) suggested that there was possibly some stagnation of the circula- 

 tion in the first pair of legs, which were very long, which the pulsating 

 organ helped to remove. 



Sir Ray Lankester said he had observed with great interest the 

 vibrating organ of Belisarius, and, if possible, he would like to see very 

 fine sections through the region concerned, in order to make sure that 

 it was really muscular. 



Mr. Scourfield replied that he showed specimens of Belisarius to 

 Dr. Warren in 1903 — which was long before the paper to which he 

 had referred was published — and Dr. Warren made sections, which he, 

 the speaker, had also examined. He did not know where they were 

 now, probably with Dr. Warren in South Africa. The examination of 

 the sections confirmed what was made oat when looking at the living 

 animal. 



Professor J. Arthur Thomson, M.A., LL.D. (Past President), 

 then delivered his paper on " Originative Factors in Evolution," which 

 will appear in extenso in the Journal. 



Sir Ray Lankester voiced the apiDreciation of all present when 

 he characterized the address as one of the best he had ever heard on 

 that difficult and profound subject of variation and heredity, presented 

 in a delightful and charming way. He referred to one point which 

 Professor Thomson did not touch, viz. that there was just as much 

 difficulty in supposing permanent stability as incessant variation. There 

 must be variation : everything was flowing, moving, changing, and the 

 aim of the Ijiologist was to determine the precise channels of variation. 



Professor Arthur Dendy agreed with Sir Ray Lankester that it was 

 marvellous that the organism should liave powers of so regulating the 

 constitution of its germ plasm that variation was largely avoided. 



