222 NATURAL HISTORY OF BHOMPSTON POND. 



latter now bearing the two respiratory tubes (a), and 

 consequently being uppermost. The future legs, wings, and 

 antennae are clearly visible on the sides of the pupa. The 

 eye-spots are now replaced by the compound eye of the adult 

 (b) ; the minute lenses of the retinulae being already formed 



The larva of another gnat, Anopheles, was found resting 

 horizontally immediately beneath the surface of the water, a 

 position which at once distinguishes it from the larva of 

 Culex (fig. 72), since the latter hangs nearly perpendicularly 

 from the surface film. Plate 4, fig. 2, is a photomicrograph 

 of the head and thorax of the Anopheles larva. It shows the 

 head with its two eye spots and beautiful brush-like mouth 

 parts. When feeding, the head, which seems peculiarly 

 movable, is turned round until the mouth parts come into 

 contact with the surface, and then by their movements 

 quantities of organisms are rapidly swept into the mouth. 



Limnochares holosericeus (fig. 75) occurs plentifully, walking 

 on the aquatic plants rather than swimming. The reddish 

 body is smooth, but the legs bear a few hairs. Finely branch- 

 ing tracheae can be seen in the unsegmented abdomen, which 

 is fused with the cephalothorax. There are several other 

 species of water mites in the pond, for instance, Arrenurus 

 globator (fig. 76). The body is truncate behind, and covered 

 with a hard integument set with protuberances. The two 

 eyes are black and placed some distance apart. 



Considering now the vertebrates, there appear to be no fish. 

 Members of both orders of Amphibia were present in the pond 

 in June, 1911 ; but apparently the hundreds of Molge (larvae) 

 perished in the July drought, when the pond was dried up. 

 This larva (fig. 78), with its external gills (a) and well developed 

 tail (Urodela), differs from the tadpole of the frog in acquiring 

 the front legs before the hind legs ; the former appear with 

 two toes, the third one developing later. Then gill-clefts 

 appear, the hind legs develop as buds (b), which later acquire 

 five toes, and a fourth toe is added to the front limb. The 

 adult form is reached after the disappearance of the gill-clefts 

 and the external gills. The circulation of the blood can be 



