86 LARVA OF TANYPUS MACULATUS. 



slowly dissolving away^ and becoming undistinguishable from the 

 mass of food-matter that fills the stomach. At the pyloric end of 

 the stomach occurs the insertion of the biliary tubes, four in 

 number, — two passing forward and two back ward, — and surrounding 

 the stomach and intestine. From this point the intestine is con- 

 tinued as a straight tube to the anus. 



In the thoracic segments succeeding the head we may discern 

 (if the larva be sufficiently grown), in addidon to the salivary 

 glands, certain cellular structures in pairs, — four on each side, as 

 shown in Fig. i8. These are the imaginal discs from which in 

 due time the legs and wings of the future fly will be developed. 



The nervous system is best seen in very young specimens. It 

 consists of a chain of ganglia united by double nervous cords, as 

 shown in Fig. ii. This, however, is wanting in the cephalic 

 ganglia, which I have not been able to make out. 



I have omitted to mention that near the extremity of the body 

 there occur two pencils of fine hairs, and that the anus is sur- 

 rounded with four fleshy appendages, the use of which I do not 

 know. They are, however, very much developed in the larva of 

 Chirono7?ius plinnosus^ known as the " blood-worm," where, I 

 think, they are concerned in the formation of its tube. 



In the month of August, 1880, I found in a pond in the 

 Crystal Palace grounds, some circular gelatinous masses contain- 

 ing eggs (as shown in Fig. 9), adherent to floadng sticks, leaves, 

 etc. I soon found that some of the egg-masses were in course of 

 development, and were producing young larvae, which I recog- 

 nised as that of Tanypiis. Whilst still in the egg, the position of 

 the eyes and the alimentary canal, as well as the segmentation of 

 the body^ could be well discerned, and they are shown in Figs. 13, 

 14, and 15. The young larva resembles the adult, but is slightly 

 thicker in proportion to its length : the alternate protrusion and 

 withdrawal of the antennae was well marked, as were also the 

 pulsations of the dorsal vessel. 



In conclusion, I should like to refer the reader to a very 

 interesting account in " The Intellectual Observer " for February, 

 1864, by the Hon. Mrs. Ward, endtled "A Windfall for the 

 Microscope," and describing certain larvae very similar, if not 

 identical, with mine ; the eggs of which, together with those of a 

 species of Phryganea^ were deposited abundantly on the sails, 

 deck, and rigging of a yacht lying at anchor in Lough Ree, co. 

 Westmeath. 



