SOME ABNORMAL ANNELIDS, 435 
Some Abnormal Annelids., 
By 
E. A. Andrews. 
With Plates 32—34. 
Amonest the Annelida, as amongst other groups of non- 
Vertebrates, various abnormalities and monstrosities may be 
found upon examining large numbers of individuals. Thus in 
some groups, as in the Eunicidz, double and supernumerary 
antenne and parapodia are not so very unusual, though they 
have received little or no attention as yet. Again, more fun- 
damental abnormalities affecting the integrity of the body 
somites occur in widely separated groups of Annelids, as has 
been recently demonstrated by C. J. Cori, T. H. Morgan, and 
F. Buchanan. Even repetitions of considerable regions of the 
body, bifurcations of the main axis that produce a double 
monster have been observed again and again. As naturally to 
be expected from the accessibility to observation and familiar 
occurrence of the terrestrial Annelids, the earthworms, it is 
chiefly amongst this group that cases of doubleness have been 
observed and recorded, though such also exist amongst the 
marine forms. 
From an examination of the bibliography of this subject as 
recently given by H. Friend,! it appears that some twenty 
cases are upon record, cases of double head or double tail, 
chiefly in the earthworms. 
In the hope that the recording and description of such cases 
may ultimately contribute to a rational comparative teratology, 
1 * Nature,’ February, 1893. 
VOL. 86, PART 4,—NEW SER. aa 
