FEKTIM'n AM) 'I 111 - ! .! J7 



The second main fact on fertiUty("genn strength") :,> developed fn,,,, obser. 

 vations on the gradations which iliis function present* in different individuals of 

 the same species, and which it may undergo in one ami the same individua 

 season, and the rate at which eggs an- produced were all found to :i |Tr,-t th. 

 or levels of fertility in pigeons. And the t\\,, sexes were here al-o f,,und to be 

 associated with fertility ("germ strength") mal.-i..- uiti .lity 



(strength), femaleness with weaker fertility. It is thi> aspect of fertilit> 

 referred to in the first quoted paragraph. 



From some of those crosses in which fertility was lowered" and the resulting 

 offspring were "predominantly male" it was noted that the "occasional" fen 

 more often appeared at or near the mil ,,f // season. .\Iore..\-.-r. -ueh results 

 more frequently obtained in such of the mating as had produced a number 



of eggs than usual, as a result of the prompt removal of th. laid 



to other birds for incubation. In other words, /v/mw/m-/, 



series, tends towards the production of female (>J^i>rimj. I.aiei ..n and 



crowded reproduction seemed each to play a part in the production of fen 

 from gametes otherwise producing only or mostly male offspring. The-e earlier 

 indications were confirmed by later work. The body of evidence bearing on U 

 points must, of course, be presented later, but we note here the fact that oft. 

 in a mating of the above sort in which the dominance of se\ is -hil'ted during tin- 

 season from maleness to femaleness, under "crowded reproduction " -otne einbi 

 are produced very late in the season not strong enough to break through the >hell; 

 and still later, embryos are produced of fewer and fewer or of no day- of develojn 

 ment. These w r eak germs, at this season, may proceed from a pair who>e earlier 

 eggs of spring and early summer produced hatchable, vigorous, and long-lived 

 birds which were mostly or only males. The Aw.s <>f fertility during the .->//. 

 involves, then, a progressive weakening of the germs themselves at'' 'ing 



from a given reduced level of fertility (germ compatibility) produced by 

 selecting consorts of distant phylogenetic relationship. There are. then, two 

 distinct kinds of things that have been called "lowered fertility": and the t\\o 

 means of obtaining a low (or a high) fertility very differently affect the production 

 of sex. 



A few paragraphs immediately following the first four given at the 1" 

 ning of this chapter bear upon this matter of "weakened germs." They \ 

 written beneath the caption: "Strength in Parents Tends to Produce Male 

 Offspring." 



"There is from pigeon crosses a preponderance of males from fir- 1 Mti of fn 



from second eggs. The first egg of the clutch may be supposed to have the advai 

 its needs are provided first, and the second egg. which is alway- the last of a clutch. 

 not quite equal chances, for it does not have first chance. 7 



"I think the first eggs of the season are certainly stronger than those coming ' 

 season. Elsewhere the early birds are the ones most highly pri/ed 1>\ i In poultry 



> ; This loss of fertility C'^rm strength ") is I,) ! observed ... nmrl, "uvnv.-rk,-,! 



they are mated to one of their own or of a very different species. I 



'Whitman writes (\V !)l thai "The male ami female have potentially the Mme cfaUM 



lags In-hind, but sometimes the mate lags," and rites Darwin's Descent of Man,Vol. II, m-. I 

 Animal Coloration. This subject is more fully treated in Volume I. ( hap- \ 1 



