334 H. S. JENNINGS 



one that had divided but twice; two whose record had stood at 3 

 fissions, six at 4, two at 5; then two at 8, two at 9, and the two 

 at 10. In the non-conjugants, the two with a record of 4 were 

 taken, three at 5, three at 6, four at 7, two at 9, and two at 10. 

 In all, 21 of the conjugant Hues and 16 of the non-conjugant Hues 

 were thus continued. Two of the former (15 and 16) were, how- 

 ever, derived originally from one ex-conjugant. 



The purpose of continuing these 37 lines was to determine 

 whether the varying rates of fission are inherited; this would show 

 that inherited differentiation had arisen within the pure line, in 

 this respect at least. 



All but one of those conjugant lines which had not divided 

 during the first week died out during the second week. Sixteen 

 of the conjugant lines and fourteen of the non-conjugant ones 

 were cultivated under identical conditions from December 6 to 

 February 27, a period of ten weeks; a few of these lines died out, 

 however, before the end of the period. It will be well to divide 

 the period into five homogeneous divisions of about two weeks 

 each, giving the fission rates for each line in each of these divisions. 

 During the first four periods the organisms were changed daily; 

 during the last one, every other day, a regimen under which they 

 did not thrive. On this account, the first four periods are more 

 characteristic and significant than the last. The fissions for 

 these five periods are given in table 33 (Appendix). I have 

 arranged them in the order of their relative rates of fission, as 

 determined by comparing the total numbers of fissions in the 

 first three periods (given in the last column). 



Examination of table 33 shows clearly that in some cases at 

 least the different rates of fission are inherited. Compare for 

 example among the conjugants, line 4 and line 15 (or 16). In 

 every one of the five periods, line 4 shows a higher rate of fission 

 than does fine 15. The same thing appears in other lines, of 

 which details will be taken up later. 



These constant differences appear in spite of the fact that all 

 of the lines were treated in exactly the same way throughout the 

 ten weeks' experiment. All were kept together, in the same 

 moist chambers, and in the same culture fluid. In order that 

 the drop belonging to one line should not have a continuously 



