244 R- ^'. HEGXER 



the summer must be enormous and must add very materially 

 to its nutriment if the organic material is absorbed as Darwin 

 seems to have proved. 



The protozoa that are able to live within the bladders are few 

 both in number of species and number of individuals. Euglenas, 

 as noted elsewhere, are rather common inhabitants. Minute 

 ciliates and flagellates as well as small amoeba? may also be 

 present. Darwin mentions that, "In all cases the bladders with 

 decayed remains swarmed with living Alg;e of many kinds, 

 Infusoria, and other low organisms, which evidently lived as 

 intruders." He does not seem to have realized that some of 

 these Infusoria might have been captives instead of intruders. 



So far as I have been able to discover the correct method of 

 capture of organisms by the utricularia bladder has never been 

 described.* Only after 69 of a total of 91 experiments were 

 carried out did I discover the significance of the compressed and 

 distended condition of the bladders, and this was finally revealed 

 to me because of the large size of the bladders borne by the plants 

 found near Bar Harbor, Maine. Paramecia were found to be 

 easily and quickly captured, but many hours were spent in 

 attempts to determine exactly how this was accomplished. The 

 bristles around the entrance seemed rather to hinder than to 

 guide them to the opening, since many specimens that might 

 have entered gave the avoiding reaction and swam away when 

 they encountered these bristles. Perhaps as Darwin suggests 

 "their use probably is to prevent too large animals from trying 

 to force an entrance into the bladder, thus rupturing the orifice." 

 Only a very few of the paramecia that swam into the entrance 

 were captured and those that were captured were taken in so 

 rapidly that it was impossible to determine whether they forced 

 their way in or the valve opened to receive them. Darwin says, 

 "Animals enter the bladders by bending inwards the posterior 

 free edge of the valve, which being highly elastic shuts again 



* Since this paper was written I have had better access to literature and find 

 that the method by which Utricularia captures its prey was more or less correctly 

 described independently by Brocker in 1911 (Ann. de Biol. Lacustre, VI), by 

 Ekambaram in 1916 (Agric. Jour. India) and by Withycombe in 1924 (Jour. Linn. 

 Soc. Bot., 46). I am indebted to Mr. A. F. Skutdi tor the reference to Brocker's 

 paper. 



