OF THE LARVA OF CORETHRA PLUMICORNIS. 69 



we find in the set of jaws and the early development of their 

 muscles the means by which its food can be obtained ; but even in 

 these muscles very little striation was evident. It required careful 

 focussing' and an accurate amount of light to make out any structure 

 in the muscular system of the first segment. The brain at this early 

 stage showed no structure, but soon minute granules made their 

 appearance, these granules ultimately becoming cells, the outer part 

 of the brain being characterised by cells of a larger size than those 

 occupying the deeper and inner parts. At the same time its colour 

 deepened to a greenish yellow tint, and exceedingly fine ramifica- 

 tions of tracheal tubes coursed through its substance. From whence 

 these tubes acquired their supply of air I could not discern. There 

 did not appear to be any connection with the air vesicles in the next 

 segment at this stage, although there is later on. The brain is 

 formed by the union of two ganglia, which give off processes to 

 supply the eyes. It is covered by a membrane, in which may be 

 seen large projecting nuclei. It is contained in a cavity, and held 

 in suspension by ligaments, which allow a certain amount of move- 

 ment, and is bathed at every pulsation of the dorsal vessel by the 

 circulatory fluid. Two nerve-cords, being the continuations of 

 ganglia forming the brain, divide in their passage from the dorsal 

 aspect of the body to the ventral, and embracing the pharynx, unite 

 below it to form the sub-cesophageal ganglion, the first of the chain 

 to which I shall presently call your attention. The next points of 

 attraction in this segment are the eyes, which arrest attention by 

 their size and blackness. They are situated one on either side of 

 the head, and appear as oval black patches encircled by clear, brilliant 

 lenses. It is not easy to see that the entire surface of the eye is 

 covered with similar lenses, and without careful opaque illumina- 

 tion they are liable to be overlooked. I have not been able to detect 

 anything like an expansion of the optic nerve to form the retina, 

 but from analogous instances in the insect world it may exist in 

 this case, although not easily seen. Situated near them are two 

 smaller black spots. These have occasionally one or two lenses, 

 similar to those in the larger eyes, irregularly placed at the edge of 

 the black, and it was only surmised that these might be considered 

 rudimentary eyes, especially as no connection apparently existed 

 between them and the brain, but by placing the larva in a shallow 

 trough which allowed it to turn, I was enabled to see under a -J- 

 of an inch power that a small branch of the optic nerve is in con* 

 Journ. Q. M. C, Series II., No. 2. Q 



