33O C. M. CHILD. 



of parts which were originally near the anterior end and possessed 

 the capacities characteristic of that region. We can make almost 

 any portion of the prepharyngeal region into a pharyngeal region 

 with corresponding change in regulatory capacity. The anterior 

 region of the second zooid, with its very high regulatory capacity 

 may be changed into the postpharyngeal region of a first zooid 

 with a great decrease of regulatory capacity. Changes of this 

 kind may be made almost at will merely by so arranging the ex- 

 periment that the part in question is brought into a certain 

 position with regard to other parts. It not only acquires a 

 different structure but its capacities are altered. These experi- 

 ments show a wide range of possibilities of influencing the mor- 

 phogenic capacities of parts indirectly through correlation. I 

 believe the point is of some general interest. In general terms 

 these experiments show that the regulatory capacity of a part 

 of the body may be altered through correlation. As regards a 

 specific case, the head, they show that a part which when iso- 

 lated originally possessed little or no capacity to form a head 

 may have this capacity greatly increased by closer association 

 with a region where a head is forming, even though the part itself 

 is not directly concerned in the formation of the head. Such facts 

 as these, possess, I believe, a certain significance in connection 

 with the problem of inheritance. In these cases we actually 

 alter the hereditary capacities of the part in question by altering 



its correlation with other parts. 





 * HULL ZOOLOGICAL LABORATORY, 



UNIVERSITY OF CHICAGO, 

 March, 1911. 



BIBLIOGRAPHY. 

 Child, C. M. 



'o6a Contributions toward a Theory of Regulation, I. The Significance of 

 the Different Methods of Regulation in Turbellaria. Arch. f. Entwicke- 

 lungsmech., Bd. XX., H. 3, 1906. 



'o6b The Relation between Regulation and Fission in Planaria. Biol. Bull., 

 Vol. XL, No. 3, 1906. 



'07 An Analysis of Form Regulation in Tubularia, I., Stolon Formation and 

 Polarity. Arch. f. Entwickelungsmech., Bd. XXIII. , H. 3. IV., Regional 

 and Polar Differences in the Time of Hydranth Formation as a Special 

 Case of Regulation in a Complex System. Ibid., Bd. XXIV., H. i. V., 

 Regulation in Short Pieces. Ibid., H. 2. VI., The Significance of Certain 

 Modifications of Regulation: Polarity and Form Regulation in General. 

 Ibid., 1907. 



