INVERTEBRATE ZOOLOGY. 63 



movements in an horizontal plane, and the right controls the up and down 

 motion. This will only .succeed with low powers, for the higher powers limit 

 the field and exaggerate the velocity. 



8. i>. Mount a drop in a loose tuft of cotton. The animals will be con- 

 fined between the threads and are easier to study. Watch their motions and 

 find out if possible by what organs they move. 



8. c- Look over several drops, if necessary, until you find a doiible one 

 like the figure 8. Watch its movements and seek to exi)lain the phenomenon. 



8. d- Staining intra vitam. If Bismark Brown be added to a drop con- 

 taining living forms, and withdrawn after a few minutes, the nuclei will be 

 found stained, the animals remaining alive. A colony maj- be kept alive sev- 

 eral days in a glass of weak Bismark Brown solution, with the same resiilt. 



9. Search among several different localities, i. e. different ponds, swamps, 

 ditches, etc. , as well as the different laboratory aquaria, for other forms of 

 Infusoria. Thej' may generally be distinguished from other forms by their 

 rapid movement. Other Protozoa and most one-celled plants move very 

 slowly or not at all. The few sessile forms show their Infusorial nature by 

 the possession of cilia and by the movements of tlie parts of the body. Forms 

 which are especially to be noted are the following : — 



(I. The trumpet form. Stcnfor, a very large green Infusorium. 



h. The ■■ Bell animalcule." The commonest forms are: (1) Vorticella, at- 

 tached by spiral stalks to leaves and stems : (2) Ejiisfylis. a large branching 

 colony with rigid stems, often fomid upon the backs of snails : (3) Coihnvnia. 

 In little cups without stalks, found upon antennae of Cyclops. 



V. Volvox — Colonies of flagellate infiisoria arranged in the form of beauti- 

 ful green globes. Look in these for sexual cells and daughter colonies. 



d. Monads — Simple flagellate forms, often green, di.stinguished by the long 

 flagellum. Many of these forms are the flagellate stage (swarm-spores) of 

 fresh water algae. 



I O. Kill a frog, open the rectum and mount in a drop of water a bit of 

 the slime from its walls. It will generally contain parasitic infusoria. Balan- 

 tidiion similar in form to l^ai-iniiocciiim. 



V. Gregarinida. 



These are vermiform unicellular forms, found as parasites in animals of 

 every class. The largest ones are visible to the naked eye, but the majority 

 are microscopic, often living within a single cell. Monocystis is a common 



