THE 
AMERICAN NATURALIST 
VOL: XAVI September, 1893. dies 2 : 309 
BIFURCATED ANNELIDS. 
By E. A. ANDREWS. 
Abnormal structures among non-vertebrates have come 
under the observation of everyone who has carefully exam- 
ined a large number of individuals in any group. Just as 
there are many cases of duplication of parts occurring among 
the higher vertebrates, so among the non-vertebrates we have 
recorded cases of the same nature. As might be expected, 
this tendency to produce supernumerary parts is most easily 
noticed in such groups as the crustacea, insects, echinoderms, 
where the nature of the skeleton aids in the recognition of 
abnormalities. Even among the soft-bodied animals, however, 
many cases of abnormal duplication of parts have been 
recorded. 
For the group Annelida, such records are scattered and not 
generally known or accessible. To bring these together with 
the hope of eventually obtaining material for a more complete 
view and discussion is the object of the present article. 
We will limit the review to cases in which the main axis of 
the worm is duplicated, to some extent, at one end of the body, 
so that the animal has there two left and two right sides, has 
either two heads or two tails.’ . 
In the last quarter of the eighteenth century Charles Bon- 
net (1), while experimenting upon the power of regeneration 
‘The author would be glad to receive references to literature upon this subject and 
bifurcations. 
if possible the privilege of examining specimens showing such bi 
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