POLYCH STA FROM THE N.E. PACIFIC. 975 
small, but the segments themselves both here and in the posterior 
region were normally developed, while there could not be the 
slightest doubt but that the anterior region was in process of 
regeneration. 
A second individual found at the same time gave another stage 
in the phenomenon. It was more nearly the normal size. The 
regions contained the following numbers of segments :— 
Anterior region...... 11 segments. 
Micdiangy sy) sack : 5 P 
Rosteniony sone... 20-30 __,, 
The anterior region thus contained nearly the normal number 
of segments, but it was shorter than usual and the peristomial 
tentacles were less than half the usual length. ‘This seemed a 
second case in which the anterior region was repeneratine. 
On returning to Cambridge, a detailed examination of a large 
amount of material preserved in formalin was made. Tube by 
tube was taken and slit up, and the length and constitution of 
the three regions noted in all the individuals contained therein. 
Jt was quite clearly shown that living constantly though the 
animals do within the shelter of a tube, regenerating specimens 
are frequently found. From an examination of these it seems 
certain that a fragment of Phyllochetopterus containing only 
segments of the median and posterior regions easily regenerates 
an entire anterior region. The number of cases in which this 
phenomenon has apparently occurred, and the fact that in their 
protected situation regeneration after external injury is an 
unlikely event, leads me to suppose that these animals have the 
power of autotomy and that it is exercised for the distinct 
purpose of reproduction. 
The tables which follow present the results of the detailed 
examination of several tubes, each represented by a separate 
TABLE L. 
Constitution of the three body regions. 
A. B. C. | Total length 
Anterior. | Median. Posterior. | of worm. 
| | 
Nas ie 2a 12 | 6 5 | 13mm. 
Piece LS ak be No ee a es 
INO; Brae cor 12 a none | 18mm, 
a | | 
(| Small regenerating stump | ?) | 
' 1 mm. long; segments | 5 39 | 
va e og | 
| 
| 
No. 3 a || not sufficiently differ- \ 
entiated to count. 
