118 SIDNEY F. HARMER. 



traordinarily resistent. After decalcification of the colonies 

 with dilute nitric acid the vesicles were practically unaffected 

 by the following reagents: — sulphuric acid (dilute and pure), 

 nitric acid (even when the strong acid is heated), strong 

 ammonia, 4 per cent, potash, ether, chloroform, benzole. 

 Gmelin's test for bile-pigments was tried without any results, 

 and the murexide test for uric acid was also negative. 



The freshly precipitated vesicles, on the contrary, were less 

 resistent. Thus, after precipitation with distilled water, 90 

 per cent, alcohol had some effect on them, while a 4 per cent, 

 solution of potash at once dissolved them. After the action 

 of corrosive sublimate (15 minutes), followed by distilled water 

 (25 minutes), even strong potash had practically no effect. 



In some cases, though not in all, ammonia added to the 

 vesicles, freshly precipitated by distilled water, first turned them 

 purplish, and then dissolved them. Certain pigmented granules 

 or cells observed in the terminal membranes of the zooecia of 

 T. plum OS a also turned purplish on adding distilled water. 



T. phalangea and T. liliacea. — Although the tentacles of 

 these species do not usually contain homogeneous vesicles, 

 they possess in their places structures which consist of a large 

 number of minute vesicles (fig. 28). Each compound vesicle 

 probably corresponds with a single cell, and its reactions are 

 different from those of the homogeneous vesicles, which occur 

 in the terminal membranes of the same species, as in T. plu- 

 mosa. The homogeneous vesicles are precipitated by various 

 reagents, and then take on the form seen in sections, whether 

 they occur in the tentacles (T. plumosa) or in the terminal 

 membranes. The compound vesicles of T. phalangea and T. 

 liliacea under no circumstances give rise to what I may call 

 the " formed " excretory vesicles. 



The tentacles of T. phalangea, as of other Cyclostomes I 

 have examined, contain pigmented granules in various parts of 

 their external epithelium. Two of these {p.) are seen in the 

 distal part of the tentacle shown in fig. 28. They do not give 

 the reactions characteristic of the other structures. 



The fresh compound vesicles of the tentacles of T. pha- 



