502 C. M. Child. 



Series I'j. Specimens of large size were selected and the at- 

 tempt made to separate each into two parts by a transverse cut 

 through the ganglia. It is difficult to make the cut in exactly the 

 desired region and in many cases it passed either anterior or 

 posterior to the ganglia. Ten specimens were finally obtained in 

 which the cut had apparently passed through the ganglia. Only 

 the anterior pieces will be considered at present. Examination 

 showed that some of these pieces contained almost the whole of 

 the ganglia and others only the anterior portions, since the cuts 

 had occurred at various levels in the ganglia. In two pieces (A) 

 the ganglia were very nearly intact, the cut having passed through 

 the posterior part (Fig. 36, the posterior line); in one piece (B) 

 about the anterior half of the ganglia seemed to be present 

 (Fig. 36, the middle line); while in the other seven (C) the cut 

 had passed through the anterior region of the ganglia leaving only 

 small parts, which in some cases protruded from the cut (Fig. 

 36, the anterior line). 



The various pieces showed a marked difference in behavior; 

 the two pieces A behaved like normal animals so far as this was 

 possible in the absenceof mostof the body, performed coordinated 

 movements and advanced rapidly, though they were not able to 

 adhere closely to the substratum since the posterior parts were 

 absent. The margins of the head were much used in the charac- 

 teristic manner for pulling the pieces forward. 



All of the remaining pieces behaved more or less like pieces from 

 which the ganglia have been removed, but, though they contained 

 parts of the ganglia, they were less active and more helpless than 

 pieces without ganglia but with parts of the longitudinal cords. 

 During the first few days after section little difference could be 

 observed between them. They made no coordinated movements, 

 could not right themselves when reversed, and in most cases 

 simply slid along over the glass by means of their cilia, making 

 irregular contractions. When the ventral surface was brought 

 into contact with the substratum attachment frequently occurred, 

 but the specimens were scarcely able to advance at all. They 

 remained attached for a time and then some muscular contraction 

 usually turned them over and they remained in that position 



