i 4 4 GRAND STRATEGY OF EVOLUTION 



expressed in different terms, or in different parental 

 powers, which ultimately serve different purposes in 

 the reproductive act. 



2. Female Attributes. In the female type of organi- 

 zation, there is usually a marked tendency to conserve 

 the surplus products of vital labor in relatively durable 

 compounds, such as fats and oils, starches, sugars, and 

 albumens. These products accumulate in the maternal 

 tissues; some of them are ultimately conveyed by the 

 bodily fluids to the ovaries and deposited in the ova as 

 an initial food supply to meet the first demands of the 

 growing embryo. From time to time, further contri- 

 butions may be made to this initial supply which are 

 conveyed by the blood, or other parental agencies, di- 

 rectly to the offspring. 



Generally speaking, the food supply stored up in 

 the egg is greatly increased with the progress of evo- 

 lution, till in birds and reptiles, for example, it reaches 

 an enormous volume. In these animals, the heavily 

 provisioned eggs are largely left to themselves; or 

 nests and shelters are built for their reception, and the 

 parents intermittently guard, or incubate them, as best 

 they may, while attending to their own welfare. 



But in the highest vertebrates, like the mammals, 

 a fundamental improvement is made in the administra- 

 tion of parental benevolence, which opens up an entirely 

 new field of progress; for it largely obviates much of 

 the inevitable waste and inherent dangers of the old 

 system. In this more economic system of the mam- 

 mals, the eggs and young are not heavily provisioned 

 beforehand. Instead they are kept within the body of 

 the mother at a constant optimum temperature; and 

 supplied with nourishment directly, and continuously, 

 from her own blood, which also carries away the waste 



