594 PROCEEDINGS OF THE SOCIETY. 



to fill up some of the gaps a few mounted and preserved specimens were 

 being shown, but- the majority of the exhibits were living specimens. 

 Personally, he could only speak about the Entomostraca, and of these 

 there were one or two forms belonging to the order Cladocera to which 

 he would like to draw attention. For instance, there was Holopedium 

 gibberum, the sole member of the family Holopedidae, which was 

 surrounded by a nearly spherical and remarkably hyaline mass of jelly. 

 This species was not to be found in the south and east of England but 

 only in certain lakes in Scotland, Ireland, and the Lake District, living 

 away from the shore, out in the open water. The meaning of the jelly 

 was not very evident, whether it served as a float or as a protection 

 against being taken for food by other animals. The jelly was probably 

 tasteless and not very nourishing and therefore not particularly palatable 

 to fishes. The remarkable persistence of the jelly was proved by the 

 fact that he had taken perfectly recognizable examples from the bottom 

 of Loch Morar, the deepest lake in the British Isles, where they had 

 possibly been for several years. 



Of the family Daphnidae there were four different genera represented, 

 viz. Daphnia, Simocephalus, Ceriodaphnia, and Scapholeberis. Species 

 of Simocephalus differed from those of Daphnia by having no shell- 

 spine and by the tip of one of the setae on the antennae being modified 

 into the form of a tiny hook, by means of which the animal could 

 suspend itself even from glass. This was explained by the fact that the 

 hooks could usually discover minute irregularities in the glass unless 

 the latter had an exceptionally good surface. Ceriodaphnia differed 

 from ordinary Daphnia by having hexagonal markings over the valves. 

 Scapholeberis was interesting because of its being the only representative 

 of the order (Cladocera) making use of the surface film. By means of 

 little hairs and scales on the flattened ventral margin it could produce 

 minute capillary depressions in the water which thus held the animal 

 suspended just under the surface. 



Another family, the Macrothricidae, was represented by a bottom- 

 loving form, Ilyocryptus agilis, incapable of proper swimming. It was 

 red in colour, which was a characteristic of bottom forms, due probably 

 to a substance resembling haemoglobin, and no doubt possessing the 

 same function of taking up and retaining a considerable amount of 

 oxygen. This species was rare— in fact the one shown was the first he 

 had seen in the Epping Forest district, in spite of much collecting 

 extending over many years. He had, however, found it on two or 

 three occasions elsewhere- — first of all in the Victoria regia tank at the 

 Royal Botanic Gardens in Regent's Park. 



The family Chydoridae, better known as the Lynceidae, was repre- 

 sented by two rather rare species, Camptocercus rectirostris and Chydorus 

 globosus. 



Lastly he might refer to a mounted specimen of Leptodora kindtii, 

 which species formed the type, and was the only representative of the 

 family Leptodoridae. It was remarkable for its large size, being nearly 

 h in. in length, and its extremely hyaline character. It lived in the 

 open water, and no doubt depended upon its transparency to enable it 

 to get into touch with its prey, which consisted of other Prntomostraca. 



