112 



PROTOPLASMIC AGE OF PROTOZOA 



The high grade of vitahty of the young protozoan is undoubtedly 

 due to the perfection of the celhilar structures and to their harmonious 

 working. This was very well illustrated in some observations on so- 

 called Paramecium caudatum (Calkins, 1906). This species has been 

 generally regarded as distinct from another very similar form, Para- 

 mecium aurelia, which is regarded as much more rare than the former. 

 The main difference between the supposed two species is the presence 



Fig. 40 



Diagram to show the relative vitahty of the caudatum and aureha forms of Paramecium. 

 The dotted Hne represents the division rate (average for ten-day periods) of an ex-conjugant 

 from the same cukure which reorganized normally, i. e., as a Paramecium "caudatum." The 

 solid line represents an ex-conjugant that reorganized abnormally, i. e., as Paramecium 

 "aurelia," but which changed into a normal form during the month of June. Note the rise 

 in division rate with the assumption of the normal condition. (After Calkins.) 



in the latter of two micronuclei as against one in the former, while 

 certain physiological differences, as indicated by the rate of division 

 and the rate of movement, were noted by Maupas ('89) and Simpson 

 ('01). The observations mentioned were made upon some ex-con- 

 jugants from a culture of the more common "caudatum" form. The 

 two cells derived from such a union were isolated, and one of them 

 was maintained for months in culture, the other dying shortly after 



