CERATIUM. NOCTILUCA. 9 



and to understand the resulting physiological division of labor. 

 (See Calkins, Protozoa, p. 232.) 



7. Consider the reasons for and against regarding Volvox 

 and allied organisms as animals rather than plants. 



Meyer: Ueber den Bau von V. aurens und V. globator. Bot. Cent., 63, 

 1895. 



CERATIUM. 



1. Examine this form with a high power, and in a favorable 

 specimen notice the sculptured outer surface of the cellulose 

 test. The living animals are green or brown owing to the pres- 

 ence of chromatophores in the protoplasm. 



2. Note the furrow encircling the body. Does it extend 

 completely around it? Is there a short furrow on one side at 

 right angles to the first, or a depression of considerable size? 

 Understand the position of the flagella. 



Draw the animal, showing the points observed. 



Look for examples of the earlier stages of division, and of 

 later stages, which appear as chains of fully formed individuals 

 attached together. 



Kofoid: Mutations in Ceratium. Bui. Mus. Comp. Zool., 52, 1909. 



NOCTILUCA. 



If living specimens are not to be had for study, material 

 preserved in alcohol, after suitable fixation, can be used. Spec- 

 imens are best examined in a cell-slide under a cover-glass. 



1. Observe the nearly globular shape, and on one side a groove 

 from which arises a large flagellum or " tentacle." Is there a deep 

 groove near it ? At the bottom of this groove it is possible to see 

 the mouth in a living specimen. Another smaller flagellum is 

 visible in living specimens inserted at the bottom of the mouth, 

 but in preserving the organism it is usually destroyed. 



2. Note the appearance of the preserved protoplasm. The 

 endoplasm appears parenchymatous. At one point a more com- 



