570 THE AMERICAN NATURALIST. (Vor. XXXV. 
(3) within the next eleven somites the supernumerary parts 
gradually diminish in size and disappear; (4) the presence 
of a slight cicatrix, anterior to the first variable metamere, 
indicates that the abnormality resulted from an injury received 
at a point where the development of new somites was in 
progress. 
The structural conditions which we have found to exist in 
this instance of partial duplication of parts throws light on the 
cases of complete bifurcation of the posterior end which have 
been frequently observed in annelids. 
Among the Lumbricidz Robertson (67) figures and describes 
a specimen of Lumdricus terrestris, the body of which is forked 
at the eighty-fifth somite. Each portion of the fork begins 
with a perfect somite, and both are borne on a single large 
metamere. A branch of the bifurcated intestine, of the chief 
blood vessel, and of the nerve trunk, is contained in each 
terminal, and the sexual organs are also fully developed. 
Bülow (83), experimenting upon the regeneration of lost 
parts in Lumbriculus variegatus Gr., discovered among the 
animals which he operated upon several specimens possessing 
two well-formed tails. In one individual 5.5 cm. long the so- 
called tails were 1.75 cm. in length. ; 
Bell (87) noted a case of bifurcation at the posterior end in 
Nerets pelagica, but gave no detailed description. 
Andrews ('92, '94) has devoted special study to bifid annelids. 
His first paper (92) reviews the literature of the subject, and 
describes among polychztes, in the family Syllidz, an individ- 
ual of the species Procerea tardigrada Wb., which possessed 
two tails of nearly equal length. In his second paper (94) he 
figures and describes two cases of the bifid condition in the 
oligochzte A//olobophora fetida, and eight cases of a similar 
abnormality in the polychzte Podarke obscura. In the ten 
specimens described there was at the posterior end complete 
duplication of the main axis of the body and all its appurte- 
nances. The only exception was an earthworm in which the 
digestive tract was absent in one of the tails. In five out of 
eight specimens of Podarke one of the terminal parts had n° 
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