108 ERNEST WARREN. 



the cell until rlie latter perishes." Vevworn mentions fatty 

 degeneration, mucous degeneration, amyloid degeneration, 

 calcification, pigment-atrophy, hyaline degeneration, and 

 colloid metamorphosis. 



Distribution op thk Pigment. 



In dealing with the different species it will be seen that all 

 the tissues of the hydroid ai-e not always involved in this 

 pigment-degeneration. Sometimes only certain tissues, or 

 particular kinds of cells, or portions of cells, are transformed. 

 Thus the stimulus does not necessarily cause pigment- 

 degeneration in all the cells of the body oi* even in all pa^ts of 

 the same cell, and this implies that it produces an effect only 

 when the protoplasm is in a certain physiological condition. 

 There is a curious tendency for the transformed cell, portion 

 of cell, or collection of cells to assume a characteristic shape 

 in the different species; e.g. in Sertularia loculosa the 

 brown pigment masses are usually more or less penr-shaped, 

 and in Sertularia operculata they may form narrow 

 streaks or a reticulum stretching through the living proto- 

 plasm of several ectodermal cells. 



Before discussing the matter further it will be well to give 

 some account of this pigment-degeneration as it occurs in 

 several species. It has been observed in various degrees of 

 intensity in the following species : 



(1) Lytocarpus filamentosus [Lain.). 



(2) Thuiaria tubuliformis {M. Turn.). 



(3) Sertularia operculata Lin. 



(4) Sertularella mediterranea Hart I. 



(5) Sertularia lineal is Warren. 



(6) Sertularia loculosa Bale. 



(7) Paragattya intermedia Warren. 



(8) Sertularia bidens Bale. 



(9) Kirch en paueria mirabilis {All man). 



