24 PROTOZOA 



Cushman: Foraminifera, Their Classification and Economic Use, 1928. 

 Farmer: Foraminifera, pp. 133-139, Lankester's Treatise. 

 Flint: Recent Foraminifera. Rep. U. S. Nat. Mus., 1897. 

 Calkins: Marine Protozoa of Woods Hole. Bull. U. S. F. C, 1901. 



ACTINOSPHAERIUM OR ACTINOPHRYS 



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

 nification as occasion demands. On account of its large size 

 it is better to study Actinosphaerium in a culture dish or 

 depression slide using the low power only. 



1. Note the many fine radiating pseudopodia. These are 

 quite stiff compared with those of Amoeba and for a con- 

 siderable time show little change, not being pushed out and 

 retracted constantly as in Amoeba. Is the animal flat or 

 spherical? 



2. Both ectoplasm and endoplasm are so filled with vacu- 

 oles that they present a frothy appearance characteristic of 

 most Heliozoa. The endoplasm of all Protozoa is alveolar 

 in structure, but in Actinosphaerium the vacuoles are ex- 

 ceptionally large, though not as large as those in the ecto- 

 plasm. In Actinophrys the endoplasm is not so sharply 

 separated from the ectoplasm. 



3. The nucleus of Actinophrys is present in the center of 

 the organism, but it is somewhat difficult to demonstrate in 

 the live animal. In Actinosphaerium there are many nuclei. 

 These can be seen well only in stained specimens. 



4. At some point near the periphery, the contractile vacu- 

 ole 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 pseudopodia extend? They may be seen to contain 



