PROTOZOA. 



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. In Ac- 

 tinophrys 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. 



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- 

 podia extend? They may be seen to contain minute granules 

 when studied with the high power and best light. 



6. If possible, observe the process of catching food with the 

 tips of the pseudopodia and the manner in which it is drawn 

 toward the body. Note any motion on the surface of the body 

 as the food is drawn closer, and also the manner in which the 

 food is finally ingested. Are there any indications that the 

 pseudopodia extend as still finer filaments beyond the point to 

 which it is possible to trace them with the highest magnifica- 



