LEE BARKER WALTON 115 



This conclusion was based on measurements of length and 

 diameter, the volume not being computed. When this 

 is done as shown in the accompanying table by utilizing 

 the formula V = y^Trld'^, thus allowing for slight decreases 

 in diameters, the facts present a different interpretation. 

 Three (a, b, c) of the four experiments dealing with a 

 "pure race" of P. aurelia indicate that the progeny of 

 the non-conjugants become larger, even when as a group 

 they are smaller (a, b?) at the beginning of the experi- 

 ment. While the fourth {d) indicates a reverse condi- 

 tion so far as the measurement of October 30 are con- 

 cerned, the measurements of the sixth and seventh genera- 

 tions immediately preceding, demonstrate that the non- 

 conjugants were larger. The result on October 30, where 

 the non-conjugants became smaller, may have depended 

 on the elimination suggested by "all existing progeny." 

 The extraordinary diminution in length (140 /x. to 123.71 

 jLt.) suggests some disturbing factor of metabolism. 



The results of the experiment with a "wild culture" 

 where progeny of "unpaired" and "paired" forms of P. 

 caiidatnm {?) were considered, again suggested to Jen- 

 nings the greater size of the progeny of the paired indi- 

 viduals (conjugants), a condition which was particularly 

 evident in the first generation. But it must be noted that 

 the disturbance of the function of conjugation in "un- 

 pairing" may have produced the result. The progeny of 

 the "unpairs" were relatively becoming larger from the 

 first to the seventh generation. These facts taken to- 

 gether with the absence of measurements of mean diam- 

 eters by which to calculate the mean volumes, suggest 

 that such a conclusion based on that part of the work 

 could not be accepted, and that the data strongly support 

 the proposition directly contrary to Jennings that the 

 progeny of conjugants tend to become smaller than the 

 progeny of non-conjugants although the latter may be 

 larger directly after conjugation as a result of slower 

 fission. Thus the evidence from various sources, although 

 incomplete, suggests that cross-bred unicellular organisms 

 are smaller than close-bred forms. 



Among multicellular organisms however it has long 



