280 



DEAN A. PACK. 



Reproduction is brought about by binary fission. Both 

 transverse and longitudinal methods of fission were observed. 

 Conjugation is followed by rapid division. At certain times, 

 perhaps after a full meal, this protozoan encysts and may remain 

 encysted for fifty days. It finally becomes active again and 

 breaks through the cyst wall as a much elongated form (see 

 Fig. 2). After swimming a short time in this form it divides 

 transversely, and if the posterior individual is not sufficiently 

 organized it rounds up into a cyst. 



Prorodon utahensis 1 (Fig. 3) is cylindrical in shape, .05 mm. 

 long, and bears an even coat of cilia. The cilia are distributed 



FIG. 4. FIG. 5. 



FIG. 4. Prorodon utahensis. Anterior end showing r, extended rods. 

 FIG. 5. Prorodon idahensis. Encysted. 



between ridges that run parallel to the long axis of the body. 

 These ridges project slightly beyond the opening of the mouth 

 (anterior end) and form finger-like projections. One of which is 

 long and well developed, being used to crowd food into the mouth. 

 The oesophagus is short and fitted with short rods that may be 

 extended in the shape of a star (see Fig. 4). The mouth and 

 oesophagus are capable of being expanded to near the diameter 

 of the body. Food vacuoles are many in number. The con- 

 tractile vacuole is large and at the posterior end. The nucleus 

 is small. The endoplasm probably contains symbiotic alga. 



This form is an active feeder. It lives on bacteria, plant cells, 

 amoebae, small ciliata, mastigamoeba, and other small protozoans 

 found in the lake. An amoeba, with a diameter fully equal to 



1 The writer has given the name Prorodon utahensis to this form, which is very 

 probably a new species. 



