H. M. FucHS 231 



there can be no reasonable question of the accidental presence of 

 spermatozoa which would vitiate the results. 



Experiments were made by Morgan to test the influence of ovary- 

 extract on the extent of self-fertilizations. In two out of eight cases 

 some of the eggs segmented, but " there may have been contamination 

 in the latter case" (9, p. 139). Again, it was tried whether water in 

 which eggs had been violently shaken would favour the self-fertilization 

 of the eggs of another individual. In several cases self-fertilization did 

 occur in the presence of such water (10, p. 325); but "There is, in fact, 

 a source of contamination in this experiment that may fully account for 

 all the cases observed. In removing the eggs from the oviduct .some of 

 the sperm from the vas deferens may be accidentally squeezed out and 

 become mixed with the eggs, and remaining in the follicle water 

 fertilize the other eggs." Whj^ were not unfertilized eggs from another 

 individual left lying in the water in which the eggs had been shaken 

 (follicle water) to test whether it contained siJermatozoa or not ? 



Again, the question recurs (11, p. 207) as to whether the few cases 

 of self-fertilization may not have been due to contamination with 

 " foreign " spermatozoa retained in the branchial basket of the animal, 

 which might then come into contact with the eggs removed from the 

 oviduct. But if unfertilized samples of these eggs had been kept as 

 controls the possible presence of such " foreign " spermatozoa would 

 have been made known. 



The repetition of such examples serves no further purpose, but in 

 conclusion it should be pointed out that some of the experiments made 

 to yield results by comparison were not comparative at all. For 

 example, eggs were fragmented by pressui-e under a cover-slip and 

 many of the eggs which had been broken in this way were self-fertilized 

 on the addition of " own " sperm, thus " indicating that the resistance 

 to self-fertilization is due to something in the membranes surrounding 

 the eggs " (10, p. 326). But the second half of the experiment, which 

 would justify such a conclusion, is missing. It is not mentioned whether 

 some of the same lot of eggs, which had not been crushed, showed no 

 self-fertilization when inseminated with an equal amount of the same 

 sperm-suspension. Again, a number of experiments were made to see 

 whether subjection of the genital products to low temperatures would 

 increase the percentages of eggs self- fertilized. In some cases a 

 considerable proportion of eggs showed self-fertilization after such 

 treatment, but apparently the second half of the experiment was again 

 missing, in which some of the same lot of eggs untreated with cold 



