92 C. M. CHILD. 



aspect of the difference in metabolic and protoplasmic condition 

 along the axis, in other words of the physiological polarity. The 

 multicellular hairs often tend to separate into their cells when the 

 gradient is obliterated or reversed, and the loss of the hairs under 

 laboratory conditions or in other unfavorable environment is 

 associated with the change in the gradient which usually occurs 

 under such conditions. 



HULL ZOOLOGICAL LABORATORY, 

 UNIVERSITY OF CHICAGO, 

 November, 1916. 



REFERENCES. 

 Child, C. M. 



'n Die physiologische Isolation von Teilen des Organismus. Vortr. u. Aufs. ii. 



Entwickelungsmech., H. XI. 

 "13 Studies on the Dynamics of Morphogenesis and Inheritance in Experimental 



Reproduction. VI. The Nature of the Axial Gradients in Planaria and 



their Relation to Antero-posterior Dominance, Polarity and Symmetry. 



Arch. f. Entwickelungsmech., XXXVII. 

 'iSa Senescence and Rejuvenescence. Chicago. 

 'i5b Individuality in Organisms. Chicago. 

 'i6a Axial Susceptibility Gradients in Algee. Bot. Gaz., LXII. 

 'i6b Further Observations on Axial Susceptibility Gradients in Algae. BIOL. 



BULL., XXXI. 

 Tobler, F. 



'02 Zerfall und Reproduktionsvermogen des Thallus einer Rhodomelacee. Ber. 



deutsch. bot. Ges., XX. 

 '04 Uber Eigenwachstum der Zelle und Pflanzenform. Jahrbiicher f. wiss. 



Bot., XXXIX. 



