INHERITANCE 325 



Study 39 . Observations on the relation between fecundity 

 and nurture. 



Materials for this study are so diverse and ever present, 

 that instead of a definite outline, the following suggestions 

 of typical illustrations are offered : 



1. In order that the enormous numbers of young pro- 

 duced by some species may be realized, study some such 

 thing as the number of spores produced by a flowering fern, 

 or seeds by a cotton wood tree. Count for example in the 

 fern the number of good spores in an average sporangium, 

 the number of sporangia on a sorus, the number of sori on a 

 fruiting frond, the number of fruiting fronds on an average 

 plant, and multiply together for totals, multiplying in the 

 end by the number of years of fruiting for the normal life of 

 the plant ; the numbers will be sufficiently significant even 

 though the last point be indeterminable. If done by a 

 class, the averaging of the collective counts will give better 

 approximation to the truth. 



2 . For observation of the reduction in numbers that goes 

 with a little parental care, compare number of young pro- 

 duced by some nesting fish, such as sunfish, bass or bull- 

 head, with those produced by a pike or a carp ; for this, ripe 

 ovaries may be taken and their content counted in part and 

 estimated (see table on page 512). 



3 . The concomitants of more extended care and careful 

 nurture may be studied by comparing the number of young 

 and the care they receive in the precocious and altricial 

 birds, abundant data for which will be found accumulated 

 and ready to hand in many good bird books. 



The record of this study may consist of a tabiilar state- 

 ment of the data obtained. 



The disturbance of the natural balance by conditions of 

 civilized life. The rate of reproduction established by 



