Heredity iti Protozoa 



587 



features are found in the progeny ? The animal has in the anterior 

 half an oral groove; near its middle a mouth; near the aboral side 

 two contractile vacuoles. How does it happen that the progeny 

 have similar structures ? If one of these structures should become 

 modified in the parent, would this modification appear in the 

 progeny ? 



For a more complex case, we have in Oxytricha (Fig. 2), a 

 definite, typical distribution of the organs of locomotion. There 

 are, for example, regularly five large setae in a row near the pos- 



m- 



Fig. I Paramecium, to illustrate the problems of inheritance in Protozoa. By mere transverse 

 fission the blunt, grooved anterior end a would be left with only one individual, the sharp posterior end 

 (p) with another, m, mouth; g, oral groove. 



terior end (S, Fig. 2). In other infusoria, related to this one, these 

 setae appear in different form, number or arrangement; How 

 does it happen that after fission the progeny have setae of the same 

 size, structure, arrangement and position as did the parent ? If 

 the parent loses one of these setae, will the reduced number appear 



