708 A. FCoate 
cellular constituents, while the posterior end of the cord is far less 
typical. The regenerated cord thus tapers posteriorly. 
NO. OF SEGMENT | 4th | 5th | th | 7th | sth 9th 
| | 
cea Gis oe ae mcr as ys cea ot sts os | 9 | 4 | legate" | ag 
AV one RC rete ees eae dia i's a enact 14 | 104 10% | 6-10 | 13} etc. units. 
IMs THN caowb eaobheonose bape nodeasot: ) a5 II 5 5 12 12] 
* Level at which old cord begins. 
In Nos. 1.30, 1.55, 1.17 and 1.22, no clear separation between the 
two parts of the regenerated cords could be made, and in some of 
the animals no sign of former injury was discernible. 
Summary 
We have shown that considerable lengths of the cord may be 
completely removed without causing the death of the animal. 
The cord so removed has attached to it the base of the 
lateral nerves, that also contain nerve cells. The rest of the lateral 
nerves have no cells. 
The removal of the cord from three or more segments completely 
shuts off from the amputated end any motor impulses and thus we 
are enabled to ascertain whether regeneration of a head is depend- 
ent on the presence of motor stimuli. 
About 50 per cent of the operated individuals regenerated a 
head (see Table 4). 
The head regenerates rather later in these operated animals than 
in the control animals. | 
The worms that did not regenerate a head showed unmistakable 
evidence of anterior growth of the nerve cord, that extended over 
several segments, and in some instances almost to the amputated 
level. 
At first the broken end of the cord was covered by a cap of small 
cells. The large ganglion cells near this end disappeared and were 
replaced by numerous minute nerve cells that migrated forward. 
These congregated into masses to form the primitive ganglia. 
The fibrous layer also tended to increase in thickness. 
