256 SfncUes iu the P/ij/s'iolo(/i/ of l-'ertilizatioii, 



The fact that self-fertilization can usually only bi' brought about at all 

 in concentrated sperm-suspension suggests that in the water containing 

 the crowded spermatozoa there may be a substance which favours the 

 self-fertilization. This cannot be connected with the reaction of the 

 water, however, as the following test shows. A milky suspension of 

 Ciona sperm was filtered. Five minutes after the suspension had been 

 made the filtrate gave the same reaction as normal sea-water with 

 neutral red and with phenolphthalein. An hour and a half afterwards 

 the latter indicator showed that a freshly filtered sample of the same 

 thick suspension was very slightly more acid than normal sea-water- 

 But, as will be shown in Part II, acid diminishes, not increases, the 

 fertilizing power of a sperm-suspension. Experiments also will be made 

 in the following way to test whether the thick sperm-suspension contains 

 substances which favour fertilization. A concentrated sperm-suspension 

 will be made up and then filtered through a porcelain filter which keeps 

 back spermatozoa. Exact comparative experiments will then be made 

 to compare the effect of this filtrate with that of ordinary sea- water on 

 the proportion of eggs fertilized by a definite concentration of sperm. 

 It may be, however, that self-fertilization takes place only with con- 

 centrated sperm-suspensions because only one .spermatozoon out of a 

 very large number has the power of fertilizing eggs derived from the 

 same individual. 



The usual (though not invariable) progressive increase in capacity 

 for self-fertilization shown by eggs and spermatozoa as they lie in sea- 

 water suggests a connection with the maturation of the eggs. Golski (7) 

 has shown that in the unfertilized egg of Ciona the first maturation 

 spindle is already formed, but the first polar body is not given off until 

 the spermatozoon has entered'. It might be that the increase in self- 

 fertility is connected with the preparation for the first maturation 

 division. At all events some change must come about in the eggs or 

 spermatozoa or both after thty have bi'cn shi-d into tht- sea-water. It 

 is very interesting to note in this coiuiection that self-fertilization can 

 only take place to a very small extent in nature. For the only time 

 that the eggs are in the presence of concentrated sperm of the same 

 individual is for the few moments alter the genital products have been 

 exuded from the ducts beibre they are ejected through the atrial 

 aperture: but at this time the eggs are usually not yet in a condition to 

 allow of any si'lf-fertilization. When tjioy hav(> reached this condition 



' I have not been able to obtain a copy of (loLsUi's iiaiHT, but beliew this .statement to 

 be correct. 



