PROTOZOA AND THE UTRICLES OF UTRICULARIA. 249 



tiny pond animal chances to rest upon this door, it immediately 

 slips through the slot which quickly closes upon the prisoner. 

 The animal swims about inside the utricle and finally dies.' 

 (2) "Larva of harlequin fly (Chironomus) just captured by plant. 

 This larva was feeding upon food particles adhering to the 

 branched spines projecting from the vesicle, and gradually 

 worked its way down the stem until it touched the slippery 

 trapdoor which straightway opened and caught it by the head. 

 Because of the downward-pointing hairs lining the vesicles the 

 struggles of the larva merely draw it further into the trap." 

 The method of capture described in these legends does not agree 

 with that I have found to be true of the species I have studied. 

 Apparently the legends were written without any actual observa- 

 tions of the process. Furthermore I know of no "downward 

 pointing hairs lining the vesicles" that might draw an insect 

 larva into the bladder. 



The most recent papers on the capture of organisms by utricu- 

 laria are by Brumpt (1925) and Langeron (1925). Brumpt notes 

 the capture of mosquito larvae by the bladders and stresses their 

 importance in the control of malaria by mosquito reduction but 

 does not discuss the method of capture. Langeron states that 

 animals penetrate easily the bladders of both aquatic and 

 terrestrial species of Utricularia and that only a slight pressure on 

 the valve is sufficient to precipitate them into the cavity, but 

 does not describe the process further. 



Organisms once captured appear never to escape. Frequently, 

 as Darwin noted, insect larvae are sometimes too long to be drawn 

 in at one time, and bladders are to be found with part of the 

 body of the larva inside and the rest projecting from the entrance. 

 Brumpt (1925) has shown that mosquito larvae are often drawn 

 in tail first and on account of their large size are usually to be 

 found with their heads extending out from the entrance. Brumpt 

 accounts for this by the habit of certain insect larvae of inserting 

 the end of the tail into crevices. In this way he supposed that 

 insect larvae forced their way into the bladders. A more simple 

 explanation, now that the method of capture is known, is that 

 the ventral brush of the anal segment which the mosquito larva 

 moves briskly in swimming stimulates the bladder to action 

 and that it is therefore the posterior end that is drawn in first. 



