152 SUMMARY OF QUERENT RESEARCHES RELATING TO 



The autozooids, though very independent, are unified in a measure ini 

 their actions by the single organ for inflation, the rhythmically con- 

 tracting peduncle, which thus serves the colony as a whole. In relation 

 to the colony the peduncle is a " super-organ." The colony exhibits 

 phosphorescence at night, but not merely by being taken during the day 

 into darkness. The phosphorescence is localized in almost microscopic 

 granulations on the surface of the rachis ; it may be excited from any 

 point by mechanical or faradic stimulation ; there must be a nerve- 

 net which controls and unifies the colonial luminosity. J. A. T. 



Pigment of Hydroids. — Ernest Warren {Annals Natal Museum,. 

 1919, 4, 103-35, 1 pi., 11 figs.). Many colonies of South African. 







n 



\ 



miwM 



Two endoderm cells of Lytocarpus filamentosus and an ectoderm 

 cell undergoing pigment-degeneration, x 1300. 



hydroids are black or very dark brown. This is due to cellular degenera- 

 tion. Senescence is an undoubted factor ; intense insolation seems- 

 operative deleteriously. The coloured granules appear to be of a 



':^' 





*-^ 



a. Ectoderm cell of Lytocarpus filamentosus undergoing pigment- 

 degeneration. B. A single granule x 5000. 



proteid nature, resulting from disturbed metaboHsm, The pigment 

 degeneration is discussed in nine species, all, as it happens, calypto- 

 blastic. The granules tend to assume characteristic shapes and aspects. 

 The whole of the protoplasm may be transformed, or the degeneration 

 changes may be confined to a particular portion of a cell. It is pointed 

 out that in the case of the disease chloasma, different types of the 



