120 SIDNEY F. HARMER. 



in spirit (which dissolves the vesicles), nor in those treated 

 with corrosive sublimate (which precipitates the homogeneous 

 vesicles) ; but colonies which have been allowed to dry, after 

 washing with fresh water, are commonly of a characteristic 

 purple colour. This colour is usually not noticeable during 

 life in T. plumosa, healthy colonies of which are yellowish ; 

 but it is conspicuous in specimens which have been dried 

 without being put in spirit. 



I have found very pale greenish, homogeneous vesicles in 

 Diastopora patina in the brown bodies, and apparently in 

 the body-cavities. These were precipitated by sublimate, 

 ammonia, or iodine in potassic iodide ; but the details of the 

 reactions were not altogether similar to those in Tubulipora. 

 I have also seen structures somewhat resembling the com- 

 pound vesicles of T. phalangea in the tentacles of a Stoma- 

 topora, perhaps S. major. 



Experiments made with indigo-carmine, carminate of am- 

 monia, and Bismarck-brown on living specimens of Tubuli- 

 pora gave only negative results. The vesicles did not appear 

 to take up any of these pigments, although control-experi- 

 ments, made with species of Bugula, gave results similar to 

 those I had previously arrived at (14). The cells which take up 

 indigo-carmine in B. flabellata are the same as the " gelbe 

 Tropfen ^' described by Claparede (4, pi. viii, fig. 1b, t.). Since 

 these are normally of a yellow or yellowish-green colour, they 

 are not unlike the homogeneous vesicles of Tubulipora. 

 They are not precipitated, however, by distilled water, iodine, 

 sublimate, or ammonia ; and taking this fact in conjunction 

 with the difference in their behaviour to indigo-carmine, it 

 may be concluded that they do not closely resemble the vesicles 

 of Tubulipora. 



The result of the previous reactions seems to be that there 

 is some substance in solution in the homogeneous vesicles 

 which is precipitated by any reagent (not being a solvent of 

 that substance) which alters the density or constitution of the 

 solvent. The action of distilled water may be due to osmosis 

 from- the- vesicle, while it is possible that substances like cor- 



