102 



Mr. A. E. Hilton : Head of Wild Bee, Andrena, showing 

 the organs of the mouth in their natural form and colour. 

 Mounted in glycerine, without pressure. 



Mr. J. B. Scriven : Two slides showing (1) Cephalic and 

 thoracic ganglia of the Blow Fly. Pupa ten days old. The 

 optic nerve shown, and also the cephalo-thoracic nerve joining 

 the two ganglia. (2) Transverse section of cephalic ganglion of 

 Blow Fly. Pupa five days old. 



Mr. A. J. French : Mounted specimens of the largest British 

 Daphnia, J), magna {= D. schaefferi Baird) S f^nd ? ; also an 

 ephippial ? of the same species. 



Mr. F. A. O'Donohoe : The suctorial ducts of the Blow Fly; 

 to show these open channels clearly, all the subjacent tissue has 

 been removed, and they are mounted without pressure in Canada 

 balsam. 



Mr. H. Morland : Brightioellia elahorata, Grev., from Oamaru 

 deposit. New Zealand, Catalogued by Grove and Sturt in their 

 Oamaru diatoms as B. indchra^ Grun., but Herr Grunow doubts 

 if this form can be differentiated from B. elahorata. First found 

 in the Barbadoes deposit in 1861, and Dr. Greville then notes 

 that he could never find peifect forms, the edges of the valves 

 being always broken, more or less. I myself have found it 

 a very fragile form, but I have come across many perfect 

 specimens. 



January 18th, 1901. 



Mr. J. Rheinberg : An arrangement for viewing the 

 colours of thin films (Newton's Pings). By pressing together 

 two pieces of plate glass, Newton's Pings are formed by the 

 intervening film of air. By the device shown, the light is reflected 

 from the right half of the ring system, and transmitted by the 

 other half. Thus the reflected and transmitted colours are 

 shown together in juxtaposition. In this way it is demonstrated 

 that the sequence of colour is the same in both cases, but that 

 the visible colours of the reflected series start half a wave-length 

 before the others. The colours of the rings which are in juxta- 

 position are approximately complementary. The colours show 

 the same sequence as those of the interference colours of Actino- 

 ci/clus Ralfsii and other diatoms, which are due to an analogous 

 principle known as "the colours of mixed plates." The rings 



