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begun about the most mature ovum (R) . By the time the 

 nest is finished, the first ovum is ordinarily complete with its 

 yolk; in the next twenty-four hours it passes down the oviduct, 

 where it receives the albumen and shell, and is emitted on the 

 day following the completion of the nest. This process is 

 repeated each day, a second egg falling into the oviduct about 

 the time the first is deposited, until the complement is com- 

 plete. The development of the ova in the migrating females 

 is much slower than that in the resident birds, as is shown in 

 the plate (T). The ova in this ovary were smaller on April 

 20 than were those of the resident bird on April 11. This 

 helps to substantiate the belief first intimated by Beal (1900), 

 that there is a direct correlation between the food and the 

 development of the reproductive organs. 



CONCLUSION. 

 In the introduction to this study, mention was made of the 

 necessity for a complete knowledge of both the environment 

 and the life history of the organism before there could be a 

 perfect understanding of the relations existing between the 

 two. The data here presented are little more than an intro- 

 duction to the facts that might be determined. So far as they 

 are known, they point toward an independent relation between 

 the Redwing and the marsh. In general, an organism is 

 dependent upon its environment for food and shelter, for 

 itself and offspring. The Redwing's independence of the food 

 supply of the marsh has been discussed. During the greater 

 part of the year it obtains its food outside of the marsh, and 

 that which it does secure here, is taken, without selection, 

 from the preponderant forms as they occur in succession. Its 

 dependence upon the marsh, or, in other words, the reason for 

 its being a marsh bird, lies in the shelter which it or its offspring 

 receive. Generalized in structure as it is, and therefore adapt- 

 able, the Redwing was able to take to the marshes when 

 crowded from its natural environment, and finding there little 

 competition, easily established itself. In its previous habits 

 it was perhaps similar to the Bobolink of to-day, and nested 

 on open uplands. It may have come to the marshes naturally, 



