THE EUGLENA 71 



(d) Examine amcebse in a drop of water on a slide, without a 

 cover glass and with the high-power ocular and the low-power objec- 

 tive. AVhat can you make of the vertical dimension? Correct any 

 errors in previous figures and make a clay model or a figure to show 

 the superficial contours. 



Exercise 3. — Special Activities. 



(e) If individual amcebse are carefully watched, it is sometimes 

 possible to observe the manner in which food is ingested and fecal 

 matter egested. Study also the contractile vacuole as it appears and 

 disappears. 



(f ) If large specimens are abundant, study the currents within the 

 endoplasm and the details of the process by which pseudopodia are 

 formed and withdrawn. Do you find the ectoplasm to consist of an 

 external membrane, the plasmalemma, enclosing a clear or hyaline 

 portion of varying thickness in different parts of the cell; and the 

 endoplasm to consist of an outer portion, the plasmagel, in which the 

 granules are held as though embedded in a gelatinous material, and an 

 innermost portion, the plasmasol, in which the granules move freely? 

 Is this separation between hyaline ectoplasm, plasmagel, and plasma- 

 sol maintained at all times and in all parts of the amoeba? Record 

 your observations in a series of three drawings showing only the 

 region of a pseudopodium. 



THE EUGLENA 

 Phylum Protozoa Class Mastigophora 



Exercise 1. — Occurrence and Activities. 



(a) Species of the Genus Euglena are common in ponds and slug- 

 gish streams, being sometimes present in such numbers as to produce 

 a reddish-green color in the ooze on the bottom or the scum on the 

 surface. If you do not have opportunity to see the material collected, 

 examine the cultures containing euglense, noting their general appear- 

 ance and the parts of the vessels in which they are most abundant. 



(b) Examine, on a slide, fresh material from a culture of euglense. 

 Look with the low-power objective for elongated green bodies which 

 may be at rest or moving about. Examine one under the high-power 

 objective and observe the form and movements. Can you determine 

 how locomotion is accomplished? Do the animals respond to light? 

 Find individuals that are contracted and others that are expanded; 



