230 Studies iti tlie Phjidoloffy of Fertilization 



p. ;^20) that the extreme difference of "/r '"''f' ")f*"/ in one combina- 

 tion in Exp. XIV anrl again in Exp. XV "is due no doubt to the faihu'e 

 to add sperm to the first lot, which might easily occur." How art' we 

 to judge of the exactness of the results of the crosses which were not 

 made twice over? The conclusion clrawn from 240 combinations was 

 that the sperm of an individual ('iaitd is not capable of fertilizing the 

 eggs of all other individuals to an equal extent, although some of the 

 results, according to Morgan, may have been due to the presence with 

 the eggs of "body-fluids." It would seem, however, that the equality 

 of conditions for each of the cro.sses should be made very much mon' 

 exact before this conclusion is justified. 



The way in which the percentages of segmenting eggs were counted 

 is not given. Nor are there usually any details as to about how many 

 eggs were used in the experiments, nor how many of these were counted. 

 In some few cases, however, the number of eggs present is given in 

 brackets after the percentages. Apparently these were the cases in 

 which exceptionally few eggs were used, as the following citations would 

 seem to show. From the 1904 paper: p. 14.5, 0°/,^ (only 3 eggs); 

 p. 149, 7, (1 egg); p. 150, 10% (only 10 eggs); p. 151, 25% (only 

 4 eggs), 50 7, (only 8 eggs), 12 7„ (only 8 eggs), etc. From the 1910 

 paper: p. 218, 100 7„ (3 eggs), 7„ (1 egg); p. 219, 100 7„ (2 eggs), 

 50 7o (2 eggs), 100 7o (4 eggs)'. How many eggs were present in the 

 other lots is not stated. 



In all work on fertilization under ditferent experimental conditions, 

 the complete absence of genital products of other individuals than those 

 used in a particular experiment is an absolutely essential condition. 

 This is, if possible, more than ever important in work on self-fertilization 

 in comparatively self-sterile organisms, where the presence of the most 

 minute trace of " foreign " spermatozoa upsets the whole results. The 

 importance of this precaution is fully realized by Morgan. He says 

 (9, p. 137), "The individuals to be used were isolated, as a rule, from 

 24 to 48 hours, and in most cases were rinsed in fi-esh-water before 

 opening," and that instruments were properly sterilized. Nevertheless, 

 throughout the work the expression of doubt recurs that such and such 

 a result may have been due to contamination with " foreign " sperma- 

 tozoa. There is no necessity for such doubt at all, for if unfertilized 

 controls are kept of every lot of eggs employed, and unfertilized eggs 

 are left lying in samples of every fluid used, if none of these segment 



' On the same page is recorded " 60% (no eggs)," hut this must be a printer's error. 



