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Updated: September 23, 2025
Animals who increase their natural protection by the addition of foreign bodies. Certain tubicolar Annelids, whose skin furnishes abundant mucus which does not become sufficiently hard to form an efficacious protection, utilise it to weld together and unite around them neighbouring substances, grains of sand, fragments of shell, etc.
Dohrn's theory with a certain added measure of equanimity after he learns this, for the marine annelids are seen, some of them, to be very beautiful creatures, quite fitted to grace their distinguished offspring should they make good their ancestral claims.
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. According to this we should have been obliged to refer them to the genus Protula.
The reproductive and digestive systems, while somewhat improved, are not very markedly higher than those of annelids. The excretory system has more work to perform and reaches a rather higher development. But in these organs there is no great or striking change; the time for marked and rapid development of the digestive and reproductive systems has gone by.
The many arguments for and against accepting the credentials of this unaristocratic ancestor cannot be dwelt upon here. But it may be consolatory, in view of the very plebeian character of the earth-worm, to know that various of the annelids of the sea have a much more aristocratic bearing.
He then found, as he did in the great majority of cases which he studied, that the phosphorescence was confined to the motor muscles, and was manifested solely when these were in the act of contracting, manifested, too, not in continuous lines along the course of the muscles, but in rows of brilliant points. More interesting than the Annelids, however, are the Alcyonarian Actinozoa.
But some of them may disappear and the others be greatly modified into awls for piercing, or a tube for sucking honey. Into the wonderful transformations of these modified legs we cannot enter. The muscles are no longer arranged to form a sack as in annelids. Transverse muscles, running parallel to the unyielding plates of chitin or horn could accomplish nothing. They have largely disappeared.
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