PRINCIPLES OF ANIMAL BIOLOGY 11 



46. Describe the general appearance of. Amoeba, its color or lack of 

 color. Be specific. 



4c. The blunt processes thrust out from the body are pseudopodia 

 (singular, pseudopodium) . Do they change shape or size? If so make 

 three sketches in outline only of the entire amoeba at intervals to show 

 these changes. What relation exists between the pseudopodia and the 

 movement of the body as a whole? In some species there is only one 

 pseudopodium. 



4d. On using high magnification note the outer clear layer of proto- 

 plasm, often quite thin; this is the ectosarc. Within the ectosarc is the 

 granular endosarc. Note the movements within these two layers, es- 

 pecially in the formation of a pseudopodium. Which layer moves more 

 rapidly when free to move? What conclusion may be drawn regarding 

 the relative fluidity of ectosarc and endosarc? Give reasons for the 

 answer to this question. 



4e. In large specimens vacuoles containing particles of food may be 

 seen. The larger food vacuoles may be recognized by their contents. 

 In which layer are they? What are their contents? These contents 

 are cell inclusions, not part of the cell. 



4/. Look for one or more pulsating vacuoles. These are not always 

 visible but if the specimen be watched for a few minutes small vacuoles 

 may be seen which increase in size and finally move to the surface where 

 they collapse. Under certain conditions of light the contractile vacuoles 

 may have a slight pinkish cast. The disappearance of the vacuole is 

 one feature that distinguishes the contractile vacuole from the more 

 persistent food vacuoles. The latter also contain food particles. 



40. Find the nucleus, a rounded, highly refractive somewhat grayish 

 body, occurring in some species in a vacuole-like structure. Is it in the 

 ectosarc or endosarc? If you do not see the nucleus clearly in your 

 specimen consult the demonstration of a stained specimen. 



4/i. Make a careful drawing of Amoeba not less than two inches in 

 diameter, showing all the structures noted in the foregoing study. Ask 

 for instructions if in doubt on any point. 



If on any point of structure or appearance your drawings fail to 

 give a proper idea, a description should be given also. 



5. How May Cells be Modified? 



5a. Cartilage Cells. On the upper end of the humerus or femur of 

 a preserved frog note the glistening white cap. This is cartilage. Place 

 a drop of water on a slide. Then with a very sharp scalpel or safety 

 razor blade shave off a very small, thin piece of cartilage from the 

 surface, and touch the edge of the blade to the drop of water. Cover, 

 and examine the thin edge of the cartilage with the microscope. How 

 are the cells arranged ? Do the cells touch one another ? The intervening 



