Changes in Salinity and Effects on Regeneration, etc. 



87 



sea-water, nor on the other hand was there any regeneration in solutions 133 

 or more per cent, with one exception to be noted later. Though regener- 

 ation occurred within these limitations, the character of the resulting 

 regenerated arms was not the same. Normal pyramid-shaped arms with 

 characteristic mouths and oral filaments were developed in the median 

 solutions only, i. e., 75 to 105 per cent inclusive. In the 70 per cent solution 



Fig. I. Thin line 

 represents regen- 5 

 eration after 14 

 days: thick line ^ 

 24 days; broken 

 line 30 days. 



3 



153 142 133 125 117 111 105 100 95 90 85 80 75 70 65 60 55 50 45 40 



the mouths were considerably reduced in number, while the number of oral 

 filaments was scarcely affected. In the 65 per cent solution there were 

 very few mouths differentiated. In the 60 and 55 per cent solutions 

 practically no mouths were formed and the oral filaments tended to clump 

 together. Similarly, beginning with the iii per cent solution, of the 

 concentrated series, the arms were increasingly atypic. In this solution 

 some arms were normal, others clumped as in the diluted solutions. In 

 the 117 per cent solution, fewer mouths were differentiated and greater 

 crowding of the oral filaments occurred. In the 125 per cent solution no 

 mouths and only very few filaments were differentiated. It is then clear 

 that while regeneration took place in a wide range of solutions, normal 

 regeneration occurred within much narrower limits, namely, 75 to 105 per 

 cent solutions. 



Corroborative results were obtained from measurement of regenerated 

 arms. Figure i and table i clearly show that when the average regeneration 

 in sea-water is taken as the norm, then the average regeneration in iii 

 to 80 per cent solutions is norm or supernorm, varying from 3.4 to 5.4 mm. 

 On either side of these limits there is a rapid decline, sharper in the more 

 concentrated solutions, far less rapid in the more dilute series. For ex- 

 ample, the average regeneration in the 117 per cent solution is less than in 

 the 50 per cent solution. 



The second series of measurements was taken 10 days after the first, 

 i. e., 24 days after removal of the arms. During these 10 days practically 

 no regeneration occurred in the concentrated solutions, while retrogression 

 set in. In all the dilute series, however, considerable regeneration occurred. 

 This is seen in figure i . Perhaps the facts are made clearer by table 2, which 



