320 ROBERT T. HANCE 



c. Immediate and temporary effect of location of the vacuoles in 

 the parent form on inheritance hy offspring 



When a paramoecium possessing the most common arrange- 

 ment of vacuoles (the supernumerary vacuoles located posteri- 

 orly) divides, the anterior half receives fewer vacuoles than the 

 posterior half. For instance, an animal with three vacuoles — 

 one anterior and two posterior — divides. Just before division 

 a new vacuole is added to each end which results in a daughter 

 .paramoecium from the anterior half with two vacuoles while 

 the daughter arising posterior to the constriction has three 

 vacuoles. The paramoecium springing from the posterior half 

 starts its life cycle with more vacuoles than does its anterior 

 mate but the anterior animal, however, as had been emphasized 

 before, has not lost the power of producing paramoecia with 

 the higher number of vacuoles. 



d. Effect of conjugation 



When conjugation was first observed it seemed that there 

 was what might be termed a selective mating or more exactly 

 that there were more two-vacuoled animals conjugating at the 

 beginning of the epidemic than multi-vacuoled individuals. 

 Further work and the final plotting of the results showed that 

 this was not the case. Neither was there a tendency for threes 

 to pair only with threes or fours with fours but there was a 

 heterogeneous mating in approximately the same percentage as 

 the frequency of the various number of vacuoles in the indi- 

 vidual units. Chart 12 illustrates these points. Conjugants 

 were found paired in nearly all possible combinations: 2x2, 

 2X3, 2X4, 2X5, 3x3, 3 X 4, 3 X 5, 4 X 4 and 4 X 5. 

 During an epidemic of conjugation the proportions of these 

 various combinations on any one day followed in a fairly close 

 manner the percentage of single animals having two, three and 

 four vacuoles in the same culture. This relation becomes clearer 

 when graphically represented as on chart 12. Here the lines 

 representing the various combinations in conjugation may be 

 seen to follow rather closely the rise or fall of the lines rep- 



