360 ALFRED GlEBS BOURNE. 



absolutely non-granular. Exceedingly careful and repeated 

 observations with a Powell and Lealand's ^^ iuch oil immersion 

 objective. Abbe's sub-stage condenser, and Engelmanu's dark 

 chamber, which last is invaluable in the glare usually pre- 

 valent here, have enabled me to ascertain with great accuracy 

 and clearness the real structure of the body substance. 



The protoplasm is throughout a perfectly colourless and 

 apparently homogeneous substance, and this substance, except 

 in the peripherally placed portions which flow out from time to 

 time to be sooner or later reabsorbed into the central mass, is 

 densely packed with spherules of a semi-fluid stroma, im- 

 pregnated with what I have ascertained to be chlorophyll, and 

 to these chlorophyll-bearing spherules the green colour of the 

 organism is due. 



In these spherules we have not to do with chlorophyll- 

 corpuscles, as they exhibit no phenomena of division, and are, 

 moreover, more fluid than chlorophyll-corpuscles. 



Their fluid character often becomes very evident after the 

 death of the organism, when some of them may be usually 

 observed to run together into larger masses. Where these 

 spherules are packed closely together they assume the form of 

 regular polyhedrons. They seem about as fluid as the stroma 

 of human red blood-corpuscles. I have come to the con- 

 clusion that they correspond to the vacuoles or, as they are 

 better termed, to distinguish them from other vacuoles, 

 vesicles, which occur in so many specimens of protoplasm 

 and give to such specimens a vesicular character. 



The fact that they contain in P. viridis a substance im- 

 pregnated with chlorophyll, a state of things hitherto un- 

 observed, has enabled me to throw some new light upon their 

 nature and upon the organization of the body substance. 



The word protoplasm is used above in the sense in which 

 Butschli^ uses the word plasma. It designates the substance 

 which Leydig speaks of as the spongioplasma, as distinguished 

 from hyaloplasma (chylema, Strasburger). In other words, 

 I consider that the substance within the vesicles is to be 

 ' liroiin, ' Protozoa,' p. 1392. 



