ABSTRACT
While studying the function of the anal gills of the mosquito larva (Wigglesworth, 1932) I had occasion to observe the effects of certain electrolytes upon them, and these effects seemed sufficiently unusual to deserve separate study. Their curious character is due, no doubt, to the unusual structure of the cells in question, but it is possible that some of these observations may throw light upon the behaviour of other types of cell in the animal body. In any case it will be desirable to record them before discussing the function of the so-called anal gills themselves.
Experiments with hypertonic NaCl have been made on certain other larvae of Diptera Nematocera (Tanytarsus sp. (Chironomidae), Dixa sp. (Dixidae), Anopheles bifurcatus, Culicella morsitans, Corethra plumicornis (Culicidae)). In all these the cells of the anal gills swelled up as in the Stegomyia larva, and the cells elsewhere in the body were unaffected.
The “artificial sea water” used had the composition : NaCl, 2-83 per cent.; KC1, 0 076 per cent. ; MgCl,, 0-501 percent.; CaCl,, 0122 per cent. No bicarbonate was added.
When the filling of the tracheoles with air takes place slowly, it is not possible to tell how far this is due to the muscular contractions caused by the asphyxiation of the larva (see Wigglesworth, 1930)
The process is not unlike plasmolysis of plant cells, particularly the abnormal type of plasmolysis described by Walter (1923) in certain marine algae, where the protoplast swells up instead of becoming separated from the cell wall. It recalls, also, the effect of hypertonic sea water on the eggs of Echinus (see Gray, 1931, p. 198) : here the salt diffuses freely into the hyaline membrane but not into the cytoplasm of the egg; hence Water is extracted from the cytoplasm, which shrinks, while the hyaline membrane swells.
