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a gelatinous mass held firmly together by threads of fibres. The eggs 

 have thick shells, which make the study of the embryological development 

 difficult to follow. The time required for hatching out is about seven or 

 eight days. Allowance should be made, perhaps, for the fact that the eggs 

 watched were not kept in running water. Development will doubtless be 

 more rapid in running water where there is plenty of air and light. It is 

 a well-known fact that the frog-spawni develops very quickly when it gets 

 air and light, but can be checked considerably by taking the spawn away 

 from these environs. The larvse when just hatched are very transparent, 

 with exoskeleton and appendages developed, but the internal structure — 

 alimentary canal, nervous, dorsal, and tracheal systems — not readily 

 traced. After a few days the larva assumes a gueyish-brown colour 

 (pei'haps due to the suspended matter in the water), which renders them 

 very opaque. The size of the larva when full grown is f in. to h in. in 

 length, which is increased when about to change into pupa. The food 

 upon which the larva subsists are diatoms, desmids, and crustaceans ; but 

 they exercise no discrimination ; so long as the food is sufficiently small it 

 passes it. When taking food the larva stands on the anal foot at right 

 angles. The hinder end of the abdomen and thorax in larva are much 

 thickened. The fore part of the abdomen is contracted ; the head also is 

 proportionately small. Eleven segments may easily be made out behind 

 the head, and on theoretical grounds we may suppose that there are one 

 or two more. Chironomus, a nearly allied species, has thirteen distinct 

 segments. Simulium has thirteen nerve centres, which give strong 

 evidence of there being thiiteen segments. The five or six segments at 

 the middle of the body are clearly defined, but the three segments of the 

 thorax and the four segments at the hinder end of the abdomen b}- being 

 distended are almost entirely obliterated. The head of the larva is 

 elongated with prominent labium in the front, arched on the inside, and 

 covered with setse of varying lengths, with eyes and accessory eyes on the 

 side, apparently mere pigment spots. The antennae are small, tapering, 

 and three-jointed. The rotatory organs, or, as they are sometimes called, 

 flabelliform appendages, are somewhat like those of culex (common gnat) 

 but better developed, and project from the side of the labium. Each is 

 furnished with about 50 setas, which may be expanded or closed up into a 

 pencil. These organs are used in feeding. When expanded there is a 

 vibrating motion, which causes a small whirlpool — the food is thus drawn 

 directly into the mouth. Should anything too large be attracted, 

 doubtless the open mandibles or jaws are brought together, which will 

 crush or liberate. When the larva is not feeding, the rotatory are folded 

 up compactly and laid down the ossophagus or gullet. The mandibles are 

 strong, curved, and tapei-iug, provided at the extreme end with 12 to 15 

 teeth, arranged in irregular rows, fringed with setse along the inner 

 margin and on the inner side. The maxillse are blunt, soft, and densely 

 clothed with setse, the inner seta; long and inclined towards the mouth. 

 The maxillary palps are two-jointed, tapering and tei'minating with a 



