PHYSIOLOGY OF THE INVERTEBRATA. i8i 



to in this chapter. Concerning the colouring matter itself, 

 it offers a greater diversity of individual pigments than the 

 blood of the Vcrtchrata. In some forms we find chlorophyll 

 and allied pigments ; while others contain one or more of the 

 following pigments : — Echinochrome, chlorocruorin, hferao- 

 cyanin, haemoglobin, and the lipochromes. 



*' To contrast the various conditions of the blood corpuscles 

 of the Iiifcrtehrata with the stages in the development of our 

 own red corpuscles is not without interest. There is a time 

 in the history of the highest mammal when there is no 

 blood developed ; there is a time when only fluid blood, 

 destitute of corpuscles, is to be seen ; possibly our blood 

 corpuscles commence as minute fragments or protoplasm 

 derived from the digested food. These minute granules may 

 coalesce in the absorbent vessels and form free nuclei ; the 

 nuclei may become surrounded by granules, a wall be de- 

 veloped on the exterior of these, and a white corpuscle (leu- 

 cocyte) would result." The colourless corpuscle, in its turn, 

 is transformed into a red corpuscle; but the history of this 

 transformation belongs to the physiology of the Vcrtrhrata 

 rather than to that of the Inccrtchmta. 



