SOME ABNORMAL ANNELIDS. 457 
metamerism can be found in the idea that “ gut-pouches” are 
the first steps. 
The questions as to the time of formation and the causation 
of such monsters remain still open. Whether they arise in the 
adult or in the embryo is as yet undetermined. Yet the balance 
of evidence seems to point to the conclusion that such bifurca- 
tions may be produced in the adult. 
While such a very unusual, in fact unique, specimen as the 
earthworm B might have arisen from such an abnormal larval 
form as figured and described by Mr. Wm. E. Ritter! for 
Polygordius, we might just as well imagine it formed as the 
result of abnormal regeneration after traumatic interference. All 
the other cases may be easily explained upon the assumption 
that removal of the normal terminal, or injury to it, has resulted 
in regeneration of such abnormal sort that more than the last 
part has been re-formed, either two complete terminals to 
replace one, or else one complete terminal instead of the 
injured part of the normal one. 
Some cases lend themselves to this explanation more easily 
than to any other ; in fact, some cannot be explained upon any 
other assumption than that the duplication has arisen in the 
adult. Such a case is that of the doubled-headed Annelid 
observed by Langerhans, which, as previously noticed,” could 
scarce have attained such dimensions without the former 
presence of a larger head that was then replaced by two small 
ones in abnormal regeneration. 
Again, in the earthworm B there are indications that the 
entire region posterior to the 59th somite has been regenerated, 
which would mean that the bifurcation was formed in a late 
stage. Then, in the eight cases studied in Podarke, anatomical 
and physiological facts point to the conclusion that in five of 
them, namely A, B, C, W, Y, one of the terminals has no, or 
no direct, nervous connection with the head-end ; while its well 
developed and large nerve-cord ends abruptly, as seen in fig. 
12, in such a way as to force upon us the idea that there was 
1 ‘American Naturalist,’ December, 1892, pp. 1047—50, 
2 *Thid., September, 1892, p. 730, 
