T. C. WHITE OX THE LARVA OF CORETHRA PLtJMICORNlS. 67 



minal segments, the first being- furnished with an elaborate plume 

 of branched hairs, four finger-shaped processes, and a set of rather 

 formidable-looking serrated hooks. We all know its beautiful 

 transparency, from which it is sometimes called the " Glass larva." 

 It is this transparency which renders it such a convenient subject 

 for observation, although the superposition of many of the internal 

 organs creates a difficulty in tracing out the developmental changes 

 which only patience and a change of position in the larva can over- 

 come. In striving to know as much about this creature's internal 

 anatomy as possible, we might be tempted to seek such ex- 

 traneous aids as can be furnished by staining fluids. ; and here let 

 me relate my experience. Corethra ■plumicorms will live in carmine 

 solution for several days, but not take the stain in the slightest 

 degree ; osmic acid of -^ per cent, strength does not seem to 

 affect it injuriously ; even acetic acid largely diluted with water 

 does not seem to act prejudicially to an existence extending over 

 some hours ; but if the internal organs are dissected out and put 

 into staining fluids, they take the colour readily. I must therefore 

 content myself by giving you the best description I am able to do 

 at present, hoping that by the patient investigations of others better 

 methods of observing the histological changes of this larva may be 

 devised. 



The particular larva of Corethra which I made the subject of 

 these observations was, when first presented to my notice, in a con- 

 dition slightly less developed than that commonly met with. 

 Diaphanous as glass, with very little differentiation of its internal 

 tissues, its muscles were visible as structureless bands of jelly 

 endowed with feeble contractility. The pulsations of its dorsal vessel 

 took place with dull and broken rhythm ; its alimentary canal had 

 but faint markings on it, scarcely pointing to its future glandular 

 character ; its brain was just indicated by a crude gelatinous mass 

 situated in a sinus posterior to the eyes, while the central gan- 

 glionic chain was only rudely mapped out by scarcely distinguish- 

 able fibres. The viscera were held in place by suspensory ligaments, 

 which stretched from them to the internal sides of the body cavity. 

 The circulatory system contained nothing of the nature of a blood- 

 corpuscle. Such, then, is a rough description of its almost rudi- 

 mentary condition at the period I commenced my observation. Day 

 by day, however, showed an alteration in the tissues, and changes 

 might have been noted even in a few hours, but when they occurred 



