BY A. G. HAMILTON. 49 



Variations of Pitchei^s. — The size is variable. I have, on culti- 

 vated plants, pitchers only 8 mm. in length with the lid open 

 and insects captured, and a small amount of liquid present. 

 Sometimes the corrugated rim is quite smooth, with only 3 to 5 

 narrow teeth standing straight up, instead of overhanging the 

 edge of the pitcher (fig. 17). 



Contents of Pitchers. — The mature pitchers contain liquid up 

 to the lower edge of the glandular surface. The quantity 

 naturally varies with the size of the pitcher. Those measured 

 contained 5, 3-2 and 2-35 ccm. I regret that a quantity collected 

 for analysis was lost by leakage. Lawson Tate gives an account 

 of the digestive principle in Cephalotiis (8), but I have not been 

 able to see his paper. The liquid is greenish-black in colour from 

 the large quantity of animal remains contained in it, but occa- 

 sionally one finds a pitcher with only a few victims, and then it 

 is quite clear. Among the debris in the pitchers, I recognised 

 wings of various insects, legs, cliitinous plates from thorax and 

 abdomen, balancers of mosquitoes, scales of moths, the claws of 

 a chelifer, living larvae of a fly, and large numbers of unicellular 

 algae, consisting of a green cell with a gelatinous envelope; it is 

 probably Protococcus^ and certainly lives and multiplies in the 

 liquid. 



While watching some plants in their native habitat, we noticed 

 flies hovering around the pitchers and occasionally entering them. 

 One of these I captured. Mr, Froggatt informs me it is one of 

 the Tabanidss. It had the appearance and blood-sucking habits 

 •of the ordinary March-fly of New South Wales. It is possible 

 that the larvae found in the liquid are those of this insect, and 

 that the individuals we saw entering it were intent upon deposit- 

 ing their eggs in the mass of digesting or decomposing insects 

 inside. In any case, the living larvse are an example of one of 

 those cases, not of symbiosis, but of one organism taking ad- 

 vantage of the conditions created by another for its own benefit. 

 There are many examples of this among insectivorous plants. 

 Geddes (9) mentions an American flesh-fly which lays its eggs on 

 the rim of Sarracenia pitchers, and the larvae when hatched make 

 4 



