m. mouth; an. anus; sg. supra-œsophageal ganglion; br. and b. provisional bristles; pr.b. præ-oral ciliated band.

The attachment of the larva by the præ-oral lobe is not more extraordinary than the attachment of a Barnacle by its head, and after such a mode of attachment the atrophy of the supra-œsophageal ganglion would be only natural.

There is one important fact which deserves to be noted in the development of the Polyzoa, viz. that if the suggestion in the text as to the mode of development of the adult from the so-called larva is accepted, the Polyzoa exhibit universally the phenomenon of alternations of generations. The ovum gives rise to a free form which never becomes sexual, but produces by budding the sexual attached form.

Bibliography.

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Entoprocta.

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Ectoprocta.

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