AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, JANUARY 19 
THE REGENERATION OF TRIANGULAR PIECES OF 
PLANARTA MACULATA. “AvSRUDY IN: POLARTTY! 
J. M. D. OLMSTED 
FOURTEEN FIGURES 
Morgan (’98), in his studies on the regeneration of Planaria 
maculata, describes two types of operation by which he was abie 
to obtain regenerated pieces in which “‘the long axis of the new 
head” was “at right angles to the long axis of the original worm.”’ 
When he cut narrow strips from the side of a planarian, he found 
that the piece, through contraction, assumed the shape of a 
crescent, the cut edge forming the concave margin. In certain 
cases all the new tissue which formed in the concavity of the 
crescent was used in the production of a head. A similarly 
shaped worm was formed in several cases when he cut from the 
side of a planarian a triangle the apex of which lay within the 
body. Both these methods of cutting, however, produced other 
pieces, which upon regeneration nearly or quite retained their 
original polarity. Morgan remarks (p. 373) ‘‘The experiments 
do not show clearly, why, at one time pieces cut from the side 
give rise to new worms having the long axis in the direction of 
the original long axis, and at other times at right angles to the 
original long axis.’ 
Child (15, p. 165) states that in triangular pieces cut from the 
side of Planaria dorotocephala the regenerated “‘head often devel- 
ops nearly or quite in the direction of the transverse axis.”’ 
The possibility of producing regenerated planarians whose polar- 
ity has apparently been so changed that their chief axis is at right 
angles to the chief axis of the worm from which they were taken 
having been demonstrated, at Dr. H. W. Rand’s suggestion a 
more detailed study of the regeneration of such pieces was under- 
‘taken, the results of which are given in this paper. 
1 Contributions from the Zoological Laboratory of the Museum of Compara- 
tive Zoology at Harvard College, No. 302. 
157 
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