CHAPTER III. 



FERTILITY AND THE SEXES.' 



"Fertility varies much in individuals of the same species, at different ages 

 and at different stages of the season. 



"The sexes in normal fertility are about even. 



"The sexes in lowered fertility show a predominance of males. 



"The sexes in much lowered fertility are males only. 



"The sexes in the lowest fertility do not appear — no offspring. 



"Lowered fertilization shows various degrees, in which development makes 

 a feeble beginning, then halts after a few days. It may run up to within a few 

 hours or days of hatching and then halt. The developmental processes may 

 also show different degrees of energy fullness, weakness, irregularities, etc., after 

 hatching. 



"When fertility is presumably not up to normal, certain colors — such as 

 white — may be exclusively female, \\niiite rings are of both sexes — but in hybrids 

 between white rings and Japanese turtles the white offspring are all females." ^ 

 (R16) 



Whitman's later studies — all of which were in evidence at the time the above 

 was written (1910) — clearly show that fertilitj' does not bear a single, simple rela- 

 tion to sex, but a sort of double relation. Indeed, the double relation which fertility, 

 or at least which "fertihty" and "developmental energy," bear to sex would at 

 first sight seem to be contradictory. 



Nowhere has Whitman written connectedly or fully on this seeming contra- 

 diction, nor has he written very extensively upon the multitude of facts and illustra- 

 tions bearing upon the second relation which he discovered that fertility bears to 

 sex. This rather meager exposition of these important results was in keeping with 

 a studied policy not to allow himself to write, or definitely to fix opinions, until 

 he had studied the facts from all possible angles of approach. In the records of 

 his last six or seven years of work, however, one finds very frequent allusions — 

 a word or a phrase— to this second relation which he found that fertility bears to 

 sex, and which at this time he undoubtedly considered as of equal or of even greater 

 importance than the earlier discovered one. Briefiy stated, this second result is 

 that, in many crosses of very distinct species or of genera, fertility (developmental 

 power) is shown to be highest in the spring and lowest in the autumn; and that vude 

 offspring predominate in the season of highest fertility, while females ' largely pre- 

 dominate in the season of lowest fertility. 



But, we ask, how can this fail to contradict the first result — compactly stated 

 above in the second paragraph under this section — which lists "much lowered 

 fertihty" as producing "only males"? It is necessary to treat this whole matter 

 immediately and at some length. 



' The editor has written this chapter; the author's statements are here placed in quotation marks. 



2 "Herbst (Arch. f. Entw. Mech. vol. 24, No. 2, 1907) thinks that resemblance to father and mother is settled 

 by the size of the copulating nuclei. If female nucleus is at highest level, the resemblance is towards the maternal 

 side. It is sheer superiority in energy." 



' Color and longevity in the offspring are also, to an appreciable extent, affected in the seasonal shift of fertility 

 and sex ; these characters, however, may to advantage be considered elsewhere. — Editor. 



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