Form Regulation in Harenactis 95 
At present it is a far cry from visible differentiation to molecular 
orientation in protoplasm. 
And finally the hypothesis is essentially speculative and the 
problems involved are practically removed from the field of inves- 
tigation by its acceptance. Consequently we are justified in 
accepting it only when the facts leave no better alternative. ‘T’o 
accept it on the basis of our present ignorance cannot serve to 
advance actual knowledge. As a stimulus to future research the 
hypothesis must affect the skeptic rather than the believer. 
BIBLIOGRAPHY 
Cuitp, C. M., ’03—Form Regulation in Cerianthus. I. The Typical Course 
of Regeneration. Biol. Bull., vol. v, no. 5, 1903. 
’°o4—Form Regulation, etc. WI. Certain Special Cases of Regulation 
and their Relation to Internal Pressure. Biol. Bull., vol. vii, 
no. 4, 1904. 
°o5—Form Regulation, etc. VIII. Supplementary Partial Discs and 
Heteoromorphic Tentacles. Biol. Bull., vol. viii, no. 2, 1905. 
’°06—The Relation Between Regulation and Fission in Planaria. Biol. 
Bull., vol. xi, no. 3, 1906. 
’°o7a—An Analysis of Form Regulation in Tubularia. I. Stolon-For- 
mation and Polarity. Arch. f. Entwickelungsmech. Bd. xxiu, 
Hing, 1907. 
‘o7b—An Analysis, etc. II. Differences in Proportion in the Primor- 
dia. Arch. f. Entwickelungsmech. Bd. xxiii, H. 3, 1907. 
‘o7-—An Analysis, etc. IV. Regional and Polar Differences in the 
Time of Hydranth-Formation as a Special Case of Regulation 
in a Complex System. Arch. f. Entwickelungsmech. Bd. xxiv, 
Hes: 1907. 
‘o7d—An Analysis, etc. V. Regulation in Short Pieces. Arch. f. 
Entwickelungsmech. Bd. xxiv, H. 2, 1907. 
‘o7e—An Analysis, etc. VI. The Significance of Certain Modifications 
of Regulation: Polarity and Form-Regulation in General. 
Arch. f. Entwickelungsmech. Bd. xxiv, H. 2, 1907. 
’o8a—Form Regulation in Cerianthus zstuarii. Biol. Bull., vol. xv, no. 
I, 1908. 
‘o8b—Regulation of Harenactis attenuata in Altered Environment. 
Biol. Bull., vol. xvi, no. 1, 1908. 
