228 STUDIES IN GENERAL PHYSIOLOGY 



volume of water contained in ordinary sea-water renders 

 regeneration impossible, the same effect is not obtained until 

 125 per cent, of fresh water has been added. 



IX. THE RELATION BETWEEN LONGITUDINAL GROWTH AND THE 

 CONCENTRATION OF THE SEA-WATER IN TUBULARIA 



1. One searches modern text-books of physiology in vain 

 for a chapter on growth; it scarcely exists even by title. 

 So far as I have been able to judge from the literature, 

 observations on the physiological conditions necessary for 

 growth in animals have been exceedingly few. I will give 

 here what I have been able to find. 



The oldest observations on the growth of animals are 

 probably made by Bonnet, who was encouraged to do so 

 through Hales' s work. 1 Bonnet measured the growth of 

 worms. The choice of material for these experiments was 

 unfortunate, as the length of these animals is subject to 

 great variations because of the contractions of the body. 

 Bonnet measured with calipers "la plus grande longueur du 

 ver," and made these values the basis of his conclusions. 

 He cut a worm into two, a second into four, a third into 

 eight parts, etc., and tried to see whether the growth of the 

 parts differed. His measurements showed "qu'il n'y a pas 

 de difference considerable entre le progres que font dans le 

 meme temps des moities et des quarts et ceux de huitiemes 

 et de dixiemes" (p. 214); and further, "que la derniere 

 portion est celle de toutes qui, en temps egal, prend le moins 

 d'accroissement, et apres elle, celles qui la precedent imme'- 

 diatement." It seems strange that the work of Bonnet stimu- 

 lated no one to repeat his experiments upon more suitable 

 material and with a better guarantee of accuracy. 



So far as I can determine, further experiments on the 

 conditions for the longitudinal growth of animals have been 



i CHAKLES BONNET, OEuvres d 'histoire naturelle et de philosophic, Vol. I, "Trait6 

 d'Insectologie " (Neuchatel, 1779), p. 193. 



