Larva of Chaoborus Crystallinus (de Geer). 
371 
together on the dorsal side of the sac only. In this position they 
receive the maximum amount of light. 
7. Experimental work carried out on larvae with collapsed air 
sacs, data not sufficiently definite to decide the hypothesis that 
Corethra larvae are gas producers. This may be proved by further 
experiments. 
* * * * * * 
The foregoing notes have accumulated during the last six years, 
and are the outcome of observations due to a general interest in 
Corethra larvae rather than definite work undertaken to establish a 
particular theory. 
To enjoy the pleasure of any interesting developments likely 
to arise whilst attempting to unravel problems presented in this 
or any other aquatic larvae, it is desirable to leave the literature on 
the subject aside. If necessary, this can be taken up when 
observations and notes have been completed, and a further pleasure 
experienced when comparison takes place, differences noted, or 
maybe agreement on points made, with results of investigation 
already recorded by other workers. 
Confirmation surely has its value as well as novelty in 
hypothesis. 
All the drawings we have made are freehand, the camera 
lucida not being employed. The value of making such records in 
assisting to understand structure must be experienced to be appre- 
ciated. On the other hand, these, as far as possible, have been 
supported by micro-photographs. 
We have mainly relied on Mr. Caffyn for the photographs of 
our mounts, and his enthusiasm in carrying out the work has 
been the means of securing many exceedingly interesting records. 
Some of these appear with this paper. 
Both Mr. Marchment and Mr. E. J. Sheppard prepared some 
very useful transverse sections of the air sacs ; but, to complete our 
detailed description of structure of these organs, we were dependent 
on a full range of transverse and longitudinal sections which 
Dr. Murray had prepared for us in his laboratory, and we are 
indebted to him for the interest taken in seeing them through. 
Bibliography. 
1. Pritchard, Andrew. — “ On the Larva and Pupa of a straw-coloured, 
plumed Culex or Gnat.” Microscopic Illustrations, 1833. 
2. Lankester, E. Ray. — “ Popular Science Review,” iv., 1865. 
3. Jones, Rymer. — “ On the Structure and Metamorphosis of the Larva 
Corethra plumicornis .” Trans. Royal Microscopical Society 
October 1867. 
4. Miall, L. C. — “ Natural History of Aquatic Insects.” London. 1895. 
5. Carrington.— “ Science Siftings,” 1868. 
