418 UTRICULAEIA NEGLECTA. Chap. XVIL 



In this latter case, as soon as the pressure is relaxed, air 

 is dra^Yn in, and the bladder recovers its proper form. 

 If it is now placed nnder 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 orifice. 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 

 bladders including decayed animals. 



In order to test this concln-ion, I experimeuted with various 

 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, including the 

 valve, collar, and antennae, were sliced off, and the condition 

 of the glands observed ; they were then irrigated, whilst beneath 

 a covering glass, with the solutions, and after a time re-ex- 

 amined with the same power as before, namely No. 8 of Hart- 

 nack. The following experiments were thus made. 



As a control experiment solutions of one part of white sugar 

 and of one part of gum to 218 of water were first used, to see 

 whether these produced any change in the glands. It was 

 also necessary to observe whether the glands were affected by 

 the summits of the bladders having been cut off. The summits 

 of four were thus tried ; one being examined after 2 hrs. 30 m., 

 and the other three after 23 hrs. ; but there was no marked 

 change in the glands of any of them. 



Two summits bearing quite colourless glands were irrigated 

 with a solution of carbonate of ammonia of the same strength 

 (viz. one part to 218 of water), and in 5 m. the i^rimordial 

 utricles of most of the glands were somewhat contracted ; they 

 were also thickened in specks or patches, and had assumed a pale 



