BY W. R. COLLEDGE. 69 



On the second day, generally the first moult occurs, but it 

 may be prolonged to the fourth. The whole of the skin and 

 appendages are thrown oft" entire, and it assumes the appearance 

 of fig. 4. So great is the difference that a casual observer 

 would not think they belonged to the same species. The head, 

 instead of being black, is now pale-yellow, and is so transparent 

 that the muscles can be traced back to their insertion in the 

 posterior part. Two dark spots indicate the eyes, and the 

 mouth brushes instead of being broad and set horizontally, are 

 now composed of a bundle of bristles equal in length, and which 

 lie reflected backwards on the outside of the cheek like a pair of 

 heavy moustachios ; and the tracheal tubes may be seen like 

 silver cords gleaming as they interlace the various structures of 

 the body. 



This first moult is a serious one for the larvfe in captivity. 

 In nature, with suitable food, sunshine and freshly oxygenated 

 water, they may do better than did my babies, for the most of 

 these did not survive the change more than a few days. The 

 transformation seems to cause physic tl exhausation from 

 which many do not recover, while some, during 

 their weakness become the prey of the numerous predatory 

 creatures which infest fresh-water pools. Water bears may be 

 seen boring their way through the intestines and brain of the 

 helpless larvffi, the muscles twitching to prove that sensation 

 was not extinct. Those that do survive grow rapidly and are 

 distinguished for a while by their transparent bodies, and their 

 size being about thrice the bulk of ordinary larvte. They are 

 rarely found in considerable numbers together, owing to the 

 scattering of the eggs and the numerous obstacles to their 

 development. Six is the largest number I have found in one 

 pool. The head brushes are composed of stout curved bristles 

 nearly equal in length. The inner curvature is lined by a row 

 of short teeth so that each bristle resembles a comb. This 

 structure is traceable in fig. 5, which is a photo of one of the 

 oral brushes. A pair of these are hinged to the upper angles of 

 the mouth, and they usually lie reflected against the cheek like 

 a pair of black moustachios. Four sets of muscles are attached 

 to them and adjacent mouth organs, and these can be traced to 

 their insertion in the back part of the head. By their means 

 these brushes are worked backwards and forwards in a curved 

 sweep. The jaws are so extensible that on contraction these large 

 brushes both disappear into the interior of the mouth. They 



