Heredity in Protozoa 6oi 



series. In the ninth generation, after eight regular alternations 

 from the anterior individual to the posterior one and back, in the 

 fissions, we should have a chain of 256 individuals, with the spine 

 on the 171st individual counting from the posterior end of the 

 chain. In the twenty-second (final) generation, the chain would 

 be 2,097,152 individuals long, and w^ould bear but a single spine 

 situated on the individual numbered 1,393,592 from the posterior 

 end.* Such a chain would be about 419 meters long, with the spine 

 about 278 meters from the posterior end.f 



Thus though the new structure is transmitted it is not multi- 

 plied, and there is no tendency to produce a race with this char- 

 acteristic. There is evidently a fundamental difference between 

 on the one hand this simple handing on of a localized structure 

 to one of the new individuals, and on the other hand, the reappear- 

 ance of the localized structure in all or many of the individuals 

 resulting from fission. The difference is in some respects similar 

 to that between "somatic" and "germinal" characters in Metazoa. 

 This point we shall take up later. 



2 The position of such a structure on the body of the individual 

 is not permanent and the same in succeeding generations. The 

 same structure is found in one generation at the anterior end, in 

 another at the posterior end; now at the middle; now in some 

 intermediate position. At first the structure alternated regularly 

 between a position nearer the posterior end, and one nearer the 

 anterior end; later its wanderings were wider. 



These fluctuations of position are due mainly to the processes of 

 growth following fission. These processes will be analyzed quan- 

 titatively in later communications; here we see merely the main 

 facts in a general way. After fission the entire body lengthens, 

 both ends pushing out rapidly. The anterior tip pushes out 

 somewhat more than the posterior one. In consequence, a struc- 

 ture located, just after fission, near the anterior end (Fig. 3, ^) is 



*The rule for finding which individual of a given generation would bear the appendage is as follows: 

 If in a certain generation the number of individuals posterior to the one bearing the spine is x, then in 

 the next generation, if the spine goes to the posterior product the number posterior to the spined individ- 

 ual will be 2x; if the spine goes to the anterior product, the number will be 2jf + i. 



■|"The length of a single individual being taken as loo/i. 



