416 PROCEEDINGS OF THE SOCIETY. 



26. Beck's Imperial. 1913. A good example of the complete 

 English model on tripod base. 



27. Swift's I.M.S. Microscope. 1913. A special design for medical 

 Bacteriology and Hsematology. This stand was specially constructed 

 for use in the Indian Medical Service. It has a built-in mechanical 

 stage. 



The Secretary moved a vote of thanks to the President, who had 

 at great personal inconvenience given two demonstrations each week. 

 It was owing to his energy that the Society had been enabled to provide 

 a striking exhibit in a most important exhibition showing the progress 

 that had been made during the war by firms associated with the produc- 

 tion of scientific material. The exhibition had a great influence on a 

 large number of people, and the demonstrations were well attended. 



The vote of thanks was carried unanimously, and it was decided that 

 the report, together with a list of the Society's exhibit, should be printed 

 in the Journal. 



The following communications were then made : — 

 In connexion with the exhibition of fresh-water Copepods, Mr. 

 Scourfield said that the Copepods, or " paddle-footed " Crustacea, 

 formed one of the divisions of the Entomostraca, and were divided into 

 three groups, typified by the genera Diaptomus, Cyclops, and Cnntho- 

 camptus, representing the families Centropagidge, Cyclopidae, and 

 Harpacticidas respectively. Apart from differences in morphology, which 

 were very well marked, the methods of swimming in the three types 

 were quite different. Diaptomus normally progressed with a gliding 

 motion brought about by the rapid vibration of the second antennge and 

 the oral appendages. During this gliding movement the long first pair 

 of antennffi were placed almost at right angles to the body, which was 

 held obliquely, back downwards. The animal could also move through 

 the water by very powerful jerks. Cyclops could not glide, but always 

 jerked about, though it was remarkable that while swimming the body 

 was held in different ways by different species, some with the back up, 

 others vertically, and others obliquely with tlie back downwards. Cantho- 

 cajnptus and its allies also jerked about, but with a peculiar zigzag spiral 

 motion. 



As a rule Diaptomus was found only in the clear w'ater of ponds and 

 lakes, but D. castor occurred in little grassy pools. Cyclops in one form or 

 another was met with in fresh water everywhere, but many of the species 

 were restricted to particular types of pond, etc. Ganthocamptus and its 

 allies were found not only in weedy ponds and ditches and the margins of 

 lakes, but certain species could usually be obtained from wet mosses 

 growing in swamps and bogs, on rocks and walls, and on posts, etc., just 

 above the surface of the water. One species he had found only in 

 the cups formed by the leaves of Bromeliaceous plants at the Royal . 

 Botanical Gardens at Regent's Park and at Kew, while another was 

 only obtained from the little collections of water in holes on tree-trunks. 



