Biological Studies on Corymorpha. 421 



proximally or distally, and according as it is heteromorphic or not. 

 The polarity of the stem is expressed, not only by the regenerative 

 development but by the changes in the axial cells. 



Locomotion is accomplished by amoeboid cells located at the 

 proximal end in the adult, more generally distributed in the larva, 

 and covering the club-shaped ends of the filaments of the 

 hold-fast. 



Cilia are present on the epithelial cells lining the hydranth 

 cavity and peripheral canals. Supplemented by contractions and 

 expansions of the hydranth cavity, they provide for the circula- 

 tory currents through the body. 



Eggs are laid both in summer and winter, usually during the 

 morning hours. They have adhesive coats. The planulae are 

 never ciliated, and their locomotion is limited to very slow creep- 

 ing movements. The larvae are geotropic. 



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Ann. and Mag. Nat. Hist., 1863, p. 1. 

 1871. — A Monograph of the Gymnoblastic or Tubularian Hydroids. 



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 CzAPEK, Fr., 1898. — Weitere Beitrage zur Kenntniss der geotropischen Reizbewe- 



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 Davenport and Perkins, 1897. — A Contribution to the Study of Geotaxis in the 



Higher Animals. Jour. Physiol., Vol. XXI, p. 22. 

 Driesch, H., 1892. — Kritische Erorterungen neuerer Beitrage zur theoretischen 



Morphologie. II. Zur Heteromorphose der Hydroidpolypen. Biol. 



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 Holmes, S. J., 1904.— The Problem of Form Regulation. Arch. Entmckl., Bd. 



XVII, p. 265. 

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