222 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
All of the arms may be pulled off and if the star is protected and fed all will 
regenerate. Such a specimen is sketched in fig. 25. This specimen was kept after the 
operation in a glass dish with frequent changes of water, and was fed upon the soft 
parts of crabs, etc. The regeneration was slow as compared with that given in the 
previous tables, the new growth shown in the figure (which is natural size) requiring 
five or six weeks, probably owing to the comparatively small amount of food taken. 
Since a mutilated arm drops off from the disk so readily, the latter nearly always 
remains intact, and in ordinary cases, therefore, if two stars were to result from oue, 
one of them must regenerate from a single arm. I have several times kept single 
arms for a long time in the aquarium or cars, but have never seen any trace of 
regeneration in them. On May 11 several arms were taken off at the usual line of 
detachment, and kept alive in the aquarium until June 9, when they showed no sign 
of regeneration. One of these was still alive on June 25, and at that time was 
apparently enjoying good health, and would turn over if put on its back. It had 
lived, therefore, for over six weeks, but showed no signs of regeneration. 
Another experiment was started on August 15; two arms were taken off from 
each of four specimens. The rate of regeneration of these specimens is given in the 
tables on p. 219. On September 10, nearly three weeks afterwards, five of the single 
arms were found alive, but showed no regeneration. On Septembers the new growth 
in the arms regenerating from the disk was from 8 to 5 mm. On September 26, six 
weeks after the operation, one of the single arms was found alive (7 mm.) It had 
not shown any traces of regenerating a new arm, although it had healed. This arm 
is represented natural size in fig. 21, b , and the new growth which took place on one 
of the stars from which these arms were detached is shown in fig. 24, a. Similar 
experiments were tried last year with the same result. In a recent article by Miss 
Helen Dean King, in Roux’s Archiv, it is stated that single arms were kept alive for 
two weeks, but never showed signs of regeneration.* 
Several experiments were carried on to determine what regeneration would take 
place if the disk were cut through. On the 11th of May 19 specimens about 24 inches 
in length were treated in the following manner: Two arms were pulled off, and at the 
base of one of the arms a piece was cut out from the top of the disk in the manner 
shown in fig. 26. These specimens were' placed in a large car at Woods Hole without 
food (except what could be carried in the water). On June 9 there was a trace of 
regeneration in some of the arms. On June 25, a little more than six weeks after the 
operation, all the arms were growing out anew, and varied from a mere trace of a new 
arm with the terminal eye-spot (which always shows first) to arms J inch (about 7 
mm.) long. This experiment shows two things: that the new arm will regenerate if 
a portion of the disk is absent, and that the rate of regeneration, like the rate of 
growth, in normal specimens, is dependent upon the nourishment, for while the new 
growth in these cars was only 7 mm. in six weeks, those which were well fed at Kick- 
ernuit gained a new growth of from 13 to 18 mm. in the same time. See page 217. 
Other experiments were tried, to determine what regeneration would take place 
if the whole star-fish were cut through in various ways, while the arms were left in 
place. It will be seen that the results were not always the same. 
In the summer of 1897 several stars about 2£ inches in length were cut through 
so as to leave three arms and part of the disk on one piece and two arms and part 
* During the summer of 1899 several single arms were kept alive from early in May until the 
middle of August, when they were destroyed by accident. There was no regeneration. 
