2i6 PHYSIOLOGY OF THE INVERTEBRATA. 



something to do with the absence of 'yellow cells' in the 

 small variety." 



{d) Sagartia (Hanthus.— The brown and white specimens 

 both contain a hpematin-yielding pigment, which is un- 

 doubtedly actiniohrematin. 



(e) Sdgartia viduata. — On extracting the ectoderm for 

 twenty-four hours in alcohol and caustic potash a yellow 

 solution was obtained. This gave a chlorophyll-like spectrum, 

 but faint traces of hfemochromogen were detected on the 

 addition of ammonium sulphide. 



(/) Sagartia 2^f(f<^(sitica. — In this species MacMunn dis- 

 covered the presence of actiniohrematin and another pigment, 

 which is different from any other he had previously examined. 

 This latter pigment is peculiar to this species. " In its 

 colour-changes with acids it has a very remote resemblance 

 to the purple pentacrinin of Professor Moseley, also to the 

 colouring matter of Ajjlysia, but differs in spectrum and 

 in some colour-changes." ''Yellow cells" are absent in 

 aS'. ])arasitica ; its colouring matter is capable of uniting 

 with oxygen and of giving it up again ; consequently it has 

 a respiratory function. 



io) Sagartia troglodytes. — The solid ectoderm of this 

 .species yielded a pigment which is related to h^mochromogen. 

 Mac]\Iunn believes that this pigment is a histohaematin. 



{h) Sagartia hcllis. — The tentacles of this species were 

 found packed with " yellow cells." The spectroscopic exami- 

 nation of the tentacles showed a banded spectrum reminding 

 one of chlorophyll, or rather chlorofucin. This spectrum 

 belongs to the mass of "yellow cells" which are embedded 

 in the endodermal linings of the tentacles. The ectoderm 

 and endoderm do not contain ha?matin. 



The examination of solutions of the tentacles revealed the 

 presence of a small amount of other pigments; but it appears 

 that the presence of the " yellow cells " has something to do 

 with the absence or suppression of respiratory pigments. 



(i) Anthea cents. — " In some specimens the ectoderm was 



