462 HEREDITY AND DEVELOPMENT 



isms, struggle between organisms and their surroundings, and 

 struggle between parts within the organism — between organs, 

 tissues, and cells. Can the formula be extended further ? 



Before we pass to Weismann's proposal to extend the concept 

 " struggle " to the determinants within the germ, it may be of 

 interest to call attention to a form of struggle and selection 

 which may be interpolated between Roux's histonal selection 

 and Weismann's germinal selection. Although Weismann does 

 not seem to favour the idea, it seems to us that there is a real 

 and important struggle between the germ-cells as such. 



1. There is a well-known struggle between potential ova. 

 In many cases the majority are sacrificed to a minority, which 

 sometimes literally feed upon their fellows. In the common 

 freshwater polyp. Hydra, and in a common marine polyp, 

 Tuhularia, only one egg-cell usually survives out of an originally 

 numerous sisterhood, reminding one of the combat to the death 

 which may occur among sister queens in a beehive. 



2. There is a kind of struggle between the hundreds of sperma- 

 tozoa in their race towards the ovum, which only one of them 

 in normal conditions will fertilise. In the familiar fertilisation 

 of frog's ova, several spermatozoa may be seen boring their 

 way through the jelly surrounding the ovum; but after one has 

 entered the ovum a rapid change in the peripheral protoplasm 

 seems to shut the door on others. It may well be, allowing 

 a margin for the purely fortuitous, that the most vigorous, 

 most sensitive spermatozoa tend to fulfil their particular office 

 of fertilising the ova, and this will tend to he to the advantage of 

 the species. Again, we are quaintly reminded of the race be- 

 tween the drone-bees to overtake the queen in her nuptial 

 flight. Usually, one drone effects sexual union, and all the 

 rest are futile. 



3. There is sometimes, according to Iwanzoff and others, 

 a struggle between ova and spermatozoa, for young ova may 

 literally digest intruding sperms. There is also a form of selection 



