V COLOUR-PHENOMENA IN WORMS 113 



the characters of the pigments, there are some inter- 

 esting facts connected with the pigmentation disclosed 

 by a series of experiments made by Mr. Sidney F. 

 Harmer. Mr. Harmer's experiments were made with 

 a view to determine the exact nature of the so-called 

 " brown bodies " of marine Polyzoa, which have been 

 supposed to be excretory; 



These brown bodies arise roughly in the following 

 way. Each polypide in the colony is only capable 

 of a relatively brief existence ; after a certain period 

 the organs, and especially the alimentary canal, be- 

 come degenerate and, fusing together into a mass, 

 form the so-called brown body which is found lying 

 inside the zooecium. The brown colour is due in 

 large part to masses of dark pigment which occur in 

 the cells of the alimentary canal. Contemporane- 

 ously with the formation of the brown body there 

 occurs in many forms a process of regeneration, 

 which results in the formation of a polypide bud, 

 and ultimately of a new individual. The brown 

 body is either eliminated by means of the gut of the 

 new polypide, or is simply stored up in the cavity of 

 the zocecium. 



In studying these processes Harmer made a series 

 of experiments with solutions of various pigments, 

 such as indigo-carmine and Bismarck-brown. His 

 method was briefly as follows : — living colonies were 

 placed in sea -water containing the pigments in 

 solution ; after a short time they were transferred to 

 clean water and the distribution of the pigment in 

 the different tissues carefully studied. The results 

 obtained differed considerably according to the pig- 

 ment employed, but in general terms it was found 



I 



