328 SEEGIUS MORGULIS 



obtained more or less systematically, agree with one another very 

 closely, and therefore point strongly to the conclusion that water 

 as a component of the organism plays a very important part in 

 its growth, and furthermore, that its quantity varies according 

 to the intensity of the process of growth, being generally the 

 greatest when growth is at a maximum. 



METHOD OF INVESTIGATION 



Impressed with the apparent parallelism between formative and 

 regenerative growth, already sufficiently expounded, I have desired 

 to find out to what extent this apparent similarity results from the 

 operation of similar factors. Of the several ways in which the inti- 

 mate relation between growth and regeneration might be studied, 

 an investigation of the water content at various stages of regener- 

 ation seemed the most available and reliable. 



My chief reason for choosing the marine polychaet Podarke 

 obscura^ as the object of these experiments, was my familiarity 

 with its regenerative process gained through previous studies. 

 While presenting in some respects great disadvantages, this worm 

 was preferred to other available animals because the curve of its 

 posterior regeneration had already been worked out in an earlier 

 contribution (Morgulis, '09). The investigation of the water con- 

 tent was conducted in the usual nianner. The live animals, 

 first dried thoroughly on filter paper, were carefully weighed; 

 then, having been dessicated over sulphuric acid, they were 

 weighed again. The complete dessication required several days, 

 and the operation was continued until the residue had attained a 

 constant weight. The quantity of water was then easily calcu- 

 lated by subtracting the second weight-determination from the 

 first. All weighings were made by means of a fine chemical bal- 

 ance weighing to one-tenth of a milligram fO.OOOl grm.) ; further- 

 more, to eliminate possible error due to any inequality in the length 

 of the arms of the balance, the difference method of weighing 

 was employed. This consists in first balancing some constant 



1 The experiments on Podarke were conducted during the summer of 1909 in 

 the laboratory of the United States Bureau of Fisheries at Vv^oods Hole, Mass. 



