338 UTRICULARIA NEGLECTA. [Chap. XVII. 



ing in a state of nature, excepting when the water is remark- 

 ably pure. 



The pedicels of the glands which are situated close to the 

 slit-like orifice, both those on the valve and on the collar, 

 are short; whereas the pedicels of the more distant glands 

 are much elongated and project inwards. The glands are 

 thus well placed so as to be washed by any fluid coming out 

 of the bladder through the orifice. The valve fits so closely, 

 judging from the result of immersing uninjured bladders in 

 various solutions, that it is doubtful whether any putrid 

 fluid habitually passes outwards. But we must remember 

 that a bladder generally captures several animals; and that 

 each time a fresh animal enters, a puff of foul water must 

 pass out and bathe the glands. Moreover, I have repeatedly 

 found that, by gently pressing bladders which contained air, 

 minute bubbles were driven out through the orifice; and if a 

 bladder is laid on blotting paper and gently pressed, water 

 oozes out. In this latter case, as soon as the pressure is re- 

 laxed, air is drawn in, and the bladder recovers its proper 

 form. If it is now placed under water and again gently 

 pressed, minute bubbles issue from the orifice and nowhere 

 else, showing that the walls of the bladder have not been 

 ruptured. I mention this because Cohn quotes a statement 

 by Treviranus, that air cannot be forced out of a bladder 

 without rupturing it. We may therefore conclude that 

 whenever air is secreted within a bladder already full of 

 water, some water will be slowly driven out through the ori- 

 fice. Hence I can hardly doubt that the numerous glands 

 crowded round the orifice are adapted to absorb matter from 

 the putrid water, which will occasionally escape from blad- 

 ders including decayed animals. 



In order to test this conclusion, I experimented with vnriotia 

 solutions on the glands. As in the case of the quadrifids, salts of 

 ammonia were tried, since these are generated by the final decay 

 of animal matter under water. Unfortunately the glands cannot 

 be carefully examined whilst attached to the bladders in their 

 entire state. Their summits, therefore, inchiding the valve, collar, 

 and antenna;, were sliced ofT, and the condition of the plands ob- 

 8erve<l ; they were then irrigated, whilst beneath a covorincj glass, 

 >ith the solutions, and after a time re-examined with the same 

 power as before, namely No. 8 of Hartnack. The following ex- 

 ]>crinient8 were thus made. 



