562 THE AMEBIC AN NATURALIST [Vol. LI 



vidual, which was 40 mm. long, was obtained among a 

 group of 47 taken from under a large rock in April, 1916.^ 

 The anterior end for a distance of 7 mm. from the tip was 

 light greenis'h yellow, with ten very feebly developed 

 tentacles ; there was a sharp line of demarcation between 

 the light yellow surface and the dark olive green of the 

 rest of the body. If H. captiva undergoes division nor- 

 mally, it can only occur in very young stages. 



With H. surinamensis, however, the case is quite dif- 

 ferent. In Table I there are summarized results of the 

 examination of several series of these animals collected at 

 different times for this particular purpose. It will be 

 noted that in these collections from 2.5 to 16.9 per cent, 

 (on the average about 11 per cent.) of the individuals 

 show a condition of either the oral or of the cloacal end 

 which is interpreted as representing regeneration. This 

 seems to be about the proportion of such instances which 

 is to be met with in general collecting, although numerical 

 records have been kept only in the cases cited. The 

 specimens represented in the tabulation were obtained 



TABLE I 



The Relative Number of Cases in which 



FOUND TO BE REGENERATING 



























June, July, 1913 



July 30, 1916 



Aug. 26, 1916 





7 



5 



- 3 



1 

 11 



10.0 

 2.5 

 13.1 

 12.8 



Jan. 31, 1917 



_^utMl 



53 



4 

 23 



5 



_ 27 



50 



16.9 

 11.2 



from one locality, Fairyland Creek, where they notably 

 a])onnd; Imt the s])ecies has been collected at many other 

 station-, where aNo tlie regenerating individuals are to 

 im' r,)uiiil in appi-o.xiniately the same proportion. The 



indicate the presence of a chemical sense (Dekge et H^rouard, 1903). 



