OF MICR O- OR GANISMS. 25 



eye of the Protista is considered as being destined to 

 perform chiefly a vegetable function. 



Klebs was able to study the structure of the ocular 

 spots, by employing a very ingenious artifice. When 

 the Euglenas are treated with a solution of sea salt, in 

 the proportion of one part to one hundred, an enor- 

 mous dilatation of the contractile vesicle, which forms 

 a hollow in the protoplasm of the animal, is induced; 

 now, as the red spot is, so to speak, glued to the vesi- 

 cle, it undergoes the same dilatation as the latter does, 

 thus greatly facilitating observation. By this treat- 

 ment it has been observed that the spot is a small dis- 

 coid or triangular mass, of jagged and irregular out- 

 line; it is formed of two material parts; for a base it 

 has a small mass of reticulated protoplasm, and in the 

 meshes of the protoplasm there are small drops of an 

 oily substance, colored red. 



This red pigment, which has received the name of 

 hematochrome, is not without its analogy with the 

 green pigment of the chlorophyl, because this latter 

 becomes red under certain conditions. For example, 

 the chlorophyl pigment which fills the entire body of 

 the Hematococcus pluinalis becomes red, when the 

 animal enters into a state of rest; the stagnant spores 

 of the algae also assume a red tint. So, also, in nu- 

 merous plants, the parts of the flower destined to be- 

 come red are green as long as they are enclosed in 

 the bud. It is thus probable that the red pigment of 

 the Euglenoids is derived from a green pigment. 



What is the physiological significance of these 

 spots? Ehrenberg considered them as eyes; hence 

 the name Euglena (word for word, pretty eye), which 

 he had given to a species of Flagellates provided with 

 ocular spots. This interpretation had been questioned 



