726 The American Naturalist. [September, 
in certain freshwater annelids (naiads) found that there was 
sometimes a sort of tubercle formed upon the body, leading, 
he imagined, to the formation of new individuals by stolon- 
like outgrowths! In one case an individual was cut into 
three pieces ; the posterior piece formed a new head for itself 
and at the same time gave rise to one of these tubercles, which 
Bonnet regarded as a second head. This specimen is shown 
in fig. 7, and its bifid anterior end in fig. 8. 
Such tubercles occurred at the posterior end also, and in one 
case, in another species of fresh-water annelid, two definite 
tails were observed. These two cases seem to have been the 
only ones noticed among very many individuals carefully 
observed during these experiments upon regeneration of parts 
after artificial section. 
Towards the middle of the present century Edward Grube 
(2) cites the case observed by Schiffer, who had made unsuc- 
cessful attempts to obtain reproduction of lost parts in the 
fresh water annelid Senuris variegatus Hoffm. 
In this one case an individual with two definite tails was 
found a few weeks after Schiffer had cut the bodies of the 
annelids into pieces in the hope of having them form new 
ends. 
More recently C. Bulow (3) made a long series of experi- 
ments upon the regeneration of lost parts in Lumbriculus var- 
iegatus Gr., and discovered among his specimens some cases in — 
which there were two well-formed tails. In one individual, 
5.5 em. long,.each tail was 1.75 em. long. 
About the same time Zeppelin (9) found three cases of 
bifurcated posterior end in the simple, perhaps primitive, 
annelid Ctenodrilus. Two of these are shown in figs. 1 and3. 
These were obtained among several hundred specimens care- 
fully examined in studying the peculiar reproduction by bud- 
ding found in the Ctenodrilide. This process consists largely 
in the reproduction of lost parts after the animal has sponta- 
neously divided itself into small pieces consisting of only a 
few somites. 
The above cases of bifurcation of the main axis in aquatic l 
oligochætous annelids have been discovered during speci 
