It becomes impossible in the matter of the complex central zone, where the exits for the larvae are contrived through the double series of overlapping leaves.

The little I have been able to learn amounts to this: The end of the abdomen, deeply cleft in a horizontal direction, forms a kind of fork, of which the upper extremity remains almost motionless, while the lower continuously oscillates, producing the foam and depositing the eggs.

The creation of the central zone is certainly the work of the upper extremity.
It is always to be seen in the continuation of this central zone, in the midst of the fine white foam gathered up by the caudal filaments.

The latter delimit the zone, one working on either side, feeling the edges of the belt, and apparently testing it and judging its progress.

These two filaments are like two long fingers of exquisite sensitiveness, which direct the difficult operation.
But how are the two series of scales obtained, and the fissures, the gates of exit which they shelter?
I do not know; I cannot even imagine.
I leave the end of the problem to others.
What a wonderful mechanism is this, that has the power to emit and to form, so quickly and methodically, the horny medium of the central kernel, the foam which forms the protective walls, the white creamy foam of the ribbon which runs along the central zone, the eggs, and the fecundating liquid, while at the same time it constructs the overlapping leaves, the imbricated scales, and the alternating series of open fissures! We are lost in the face of such a wonder.