ACTINOSPELERIUM OR ACTINOPHRYS. 5 



the sand beaches of such islands as the Bermudas may be had 

 for study. Examine them with a low power by reflected light. 



1. Carefully examine various shells, compare them with each 

 other and with figures. Notice the great variety in size and 

 shape and determine how the chambers must have been added 

 during growth. 



2. Observe a single opening in a shell, and determine whether 

 the general surface has any finer perforations. Be sure to under- 

 stand the relation of the live animal to the shell. (Refer to 

 Calkins, pp. 71-78, for a general discussion of the shells of the 

 Sarcodina.) 



Make drawings of several types of shells. 



ACTINOSPHAERIUM OR ACTINOPHRYS. 



Find, as usual, with the low power, and increase the magni- 

 fication as occasion demands. 



1. Note the many fine radiating pseudopodia. These are quite 

 stiff compared with those of Amceba and for a considerable time 

 show little change, not being pushed out and retracted constantly 

 as in Amceba. Is the animal flat or spherical? 



2. Both ectoplasm and endoplasm are so filled with vacuoles 

 that they present a frothy appearance characteristic of most 

 Heliozoa. The endoplasm of all Protozoa is alveolar in struc- 

 ture, but in Actinosphaerium the vacuoles are exceptionally 

 large, though not as large as those in the ectoplasm. 



3. The nucleus is present in the center of the organism, but 

 it is somewhat difficult to demonstrate in the live animal. 



4. At some point near the periphery, the contractile vacuole 

 can usually be seen. When it is found notice its action, and 

 immediately after it has contracted look among the pseudopodia 

 of that region for indications of its extruded contents. 



Draw a specimen, indicating all of the points observed. 



5. When the contractile vacuole discharges, or when any 

 foreign body touches the ends of the pseudopodia, notice the 

 way in which this type of pseudopodium is moved. What does 

 this indicate in regard to its structure ? How far do the pseudo- 



