128 GENERAL BIOLOGY 



There is also a red dot, called an eye-spot or stigma, close to the 

 reservoir, near the inner end of the gullet. It is made up of small 

 granules of haematochrome ( ). Because the an- 



terior end of the animal seems to be more sensitive to light than other 

 parts, it is supposed that this red stigma functions somewhat as an eye. 

 It has also been suggested that this red haematochrome is not the sensi- 

 tive part at all but that the protoplasm immediately beneath it is. As 

 haematochrome has many of the characteristics of pigment granules 

 of the eyes of higher animals, it is likely that we meet here with a sort 

 of beginning eye. 



There is a single nucleus a little posterior to the center of the body. 

 It has a distinct membrane. On the inside of the nucleus there is a so- 

 called nucleolus. However, as this latter functions as a division center 

 it is probably not a nucleolus. 



There are a number of oval discs called chromatophores ( ) 



suspended in the protoplasm. These contain chlorophyl. In Euglena 

 we meet with our first example of photosynthesis ( ). 



A little later, when plant-life is studied, it will be noted that this is the 

 accepted method among plants of manufacturing their food. Photosyn- 

 thesis means that "the chlorophyl is able, in the presence of light, to 

 break down the carbonic acid (CO 2 ), thus setting free the oxygen, and 

 to unite the carbon with water, forming a substance allied to starch 

 called paramylum ( ). If specimens are kept in 



good light continually a large amount of paramylum will be stored up 

 for future use, being laid down around some granules of proteid sub- 

 stance near the center of the body. These granules are called pyrenoids 

 ( ). Both the pyrenoids and chromatophores are 



permanent cell structures and increase in number by division and not by 

 the origin of new ones from the other parts of the body." 



LOCOMOTION 



The animal moves by means of its flagellum, which appears as a 

 single whiplike structure, although really it is composed of four separate 

 fibrils wound together. This flagellum begins in the body proper and 

 extends through the wall of the mouth depression. It is often as long 

 as the animal itself. In addition to the assistance rendered the animal 

 in locomotion by this appendage, the entire animal is elastic, contracting 

 and expanding, so that the body looks much like a worm in movement. 



NUTRITION 



As already stated, Euglena is like a plant in that it possesses 

 chlorophyl and manufactures its own food. When an animal manu- 

 factures its food in this way it is said to be holophytic ( ). 

 But as Euglena can live in the dark, and chlorophyl does not permit 

 the manufacture of food without light, the animal must be able to feed 



