CELLULAK DEGENMRA'I'IOX AND FORMATION OF PIGMENT. 127 



was noticed in the endodenn of Kirchonpaueria inira- 

 bilis {Allman), and a suggestion of the same was seen in 

 S e r t u 1 a r i a a c a n t h o s t o ni a Ba le. 



C03[PAKATIVE KeVIKW AND CONCLUSIONS. 



In the present paper there has been described a number 

 of examples of cellular degeneration in the tissues of certain 

 hydroids, resulting in a general black or dark brown colora- 

 tion of the entire colony. Only calyptoblastic hydroids have 

 been found to be thus affected ; but probably this is purely 

 accidental, owing to the fact that the available material of 

 gymnoblastic species is mostly sparse. 



The cause or causes of this pigment-degeneration in the 

 tissues have not been definitely ascertained ; but bacteria or 

 other parasites do not appear to be present, and there is some 

 evidence for suspecting that intense insolation, especially 

 when acting on an old colony, is at least one of the causes, if 

 not the primary cause. 



The cellular degeneration involves different cells and 

 tissues in the various species of hydi'oids examined, and there 

 is, so to speak, a specific kind of degeneration in each 

 species. The degeneration processes lead to the formation of 

 of black or dark brown granules of characteristic shape and 

 appearance and attaining to a more or less definite maximum 

 size, and the cells, clusters of cells, or portions of cells, pro- 

 ducing the granules tend to assume a characteristic shape 

 and aspect. It would be quite easy to name the hydroid by 

 an examination of the degenerated areas. Sometimes in 

 place of the occurrence of discrete pigment granules, mode- 

 rately large homogeneous masses of dark brown or black 

 substance arise by the fusion of the granules, and these 

 masses may tend to have a characteristic shape and size. 



Microchemical tests indicate that the coloured granules or 

 masses which are formed are of a proteid nature. Under the 

 microscope the granules sometimes have the appearance of 

 small globules of coloured fat, but osmic acid has no particular 



