12 MATHILDE M. LANGE 
three well-developed suckers (arranged in single file), and a 
distal part which compared to the proximal part is exceedingly 
thin. Naef has called this lash-like appendage a flagellum. The 
three suckers are arranged in single file and remain so perma- 
nently. In a more advanced stage the arm is provided with a 
larger number of suckers, of which the first three still are in 
single file, while the others are arranged in zig-zag fashion. Here 
we have an arrangement similar to that in figures 13 and 14. 
So we may safely say that the arrangement of the first newly 
formed suckers in the course of regeneration does not differ 
greatly from the arrangement of the first suckers in the course 
of normal development. In regenerated parts, however, only 
one sucker remains permanently without a partner. In some 
cases I have found from two to three suckers arranged in this 
manner. The single sucker at the base of the regenerated part 
was to be found in even such advanced stages of regeneration 
where it was difficult to distinguish between the old stump and 
the newly formed part. Brock believes that this single sucker 
only appears after the lost part has been completely regenerated. 
On page 592 he speaks of it as follows: 
Ist die Einschniirung (an der Amputationsstelle) bereits bis auf die 
Furche verschwunden, und geht der regenerierte Arm schon ganz 
unmerklich in den Stumpf tiber, so verr&t sich der Vorgang der Regen- 
eration noch lange durch eine mehr oder minder breite Liicke in der 
Reihe der Saugnapfe gerade an der Amputationsstelle, welche erst 
ganz zuletzt von einem an dieser Stelle hervorsprossenden Saugnapf 
ausgeftillt wird. 
Brock arrived at these conclusions through the study of several 
regenerated arms which he found on animals caught in the Indian 
Ocean. He never tried to prove his assertions by experiment. 
T should like to draw attention to the fact that never in the course 
of my investigations (and I had quite a quantity of material 
at my disposal) was I able to detect an interval in. the row of 
suckers such as Brock both illustrates and describes. The sucker 
which Brock believes to be the last is probably identical with 
the single sucker at the base of the regenerated part (figs. 15 
and 16). This sucker, however, is by no means the last, but 
