(FIGURES 65 TO 67. Young Tubicolar worms, magnified with the simple lens
about 6 diam.:
FIGURE 65.* Without operculum, Protula-stage. (* Figure 65 is drawn from
memory, as the little animals, which I at first took for young Protulae,
only attracted my attention when I remarked the appearance of the
operculum, which induced me to draw them.)
FIGURE 66. With a barbate opercular peduncle, Filograna-stage;
FIGURE 67. With a naked opercular peduncle, Serpula-stage.)
One of the simplest examples is furnished by the development of the
Tubicolar Annelids; but from its very simplicity it appears well adapted
to open the eyes of many who, perhaps, would rather not see, and it may
therefore find a place here. Three years ago I found on the walls of one
of my glasses some small worm-tubes (Figure 65), the inhabitants of
which bore three pairs of barbate branchial filaments, and had no
operculum. According to this we should have been obliged to refer them
to the genus Protula. A few days afterwards one of the branchial
filaments had become thickened at the extremity into a clavate operculum
(Figure 66), when the animals reminded me, by the barbate opercular
peduncle, of the genus Filograna, only that the latter possesses two
opercula. In three days more, during which a new pair of branchial
filaments had sprouted forth, the opercular peduncle had lost its
lateral filaments (Figure 67), and the worms had become Serpulae.
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