1892.] Bifurcated Annelids. 727 
researches upon these small and not commonly observed ani- 
mals. In their terrestrial allies, however, among the well 
known earthworms, cases of such striking monstrosities have 
fallen under the observation of many casual observers. 
In Europe Charles Robertson (4) described and figured 
such a case in Lumbricus terrestris. As shown in figs. 4 and 5 
the body is divided into two equal posterior parts, at the 85th 
somite. Each begins with a perfect somite and thus leaves a 
triangular membranous area on the dorsal and ventral sides of 
the trunk. The length to the fork was two inches; that of each 
caudal portion $ inch. Each portion had about 20 somites 
and contained a portion of the forked intestine, chief blood 
vessels and nerve trunk ; had well developed setæ and a sepa- 
rate anus. The animal appeared to be an adult, having fully 
and normally developed sexual organs. 
This description was drawn from an alcoholic specimen in 
the Oxford University Museum. F. Jeffrey Bell (5), however, 
had a live specimen of the same species under observation for 
two months. This was a small immature individual repre- 
sented in figs. 10, 13 and 14, in which, however, the clitellum 
began to appear shortly before death. Before dying, the left 
tail, which was shorter, became less and less active and rela- 
tively shorter till finally both tails were thrown off or disap- 
peared and death ensued. 
He also observed a dead specimen of L. fetidus in which 
there was a forked posterior end. 
Horst (6), in experimenting upon regeneration of lost parts 
in earthworms, found one 100mm. long with two tails, each 
25 mm. long and quite normally formed. This again was a 
living specimen when observed. 
On this side of the Atlantic, Asa Fitch (7) seems to have 
been the first to record the occurrences of such monstrosities. 
Among some interesting observations upon the habits of 
earthworms, regarded as L. terrestris, he records finding in his 
garden in New York State, a live specimen about three inches 
long with the posterior end divided for nearly one fourth of 
this length. These appendages are equal, but each only about 
two-thirds the normal thickness of the body anterior to them. 
j 
