Monograph of the Fresh-Water-Polyzoa, Including All the Known Species, Both British and Foreign (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1856 edition. Excerpt: ...to follow them further. In the afferent Trembley, 'Memoires pour servir a l'Histoire d'un genre de Polypes d'eau douce/ Leyde, 1744. quent observers. Trembley has demonstrated a complete alimentary canal, consisting of oesophagus, stomach, and intestine; but though he has seen the emission of the excrementitial matter from the intestine, the actual termination of this tube has escaped him. He has observed the retractor muscles, and has noticed the funiculus attached to the fundus of the stomach; this last organ, however, he supposes to be a muscle destined, like the true retractors, for the withdrawal of the polypide into its cell. He has shown the connection between the polypide and its cell, and demonstrated that the former ought not to be viewed as the mere fabricator of the latter, as the caddis worm is of his case, but that each is an inseparable part of one and the same animal. He witnessed also the circulation of the fluid in the perigastric space. This circulation was rendered evident by the presence of small spherical bodies, which were kept in continual motion, and were often propelled from one cell into a neighbouring one; a fact which at once led him to infer the continuity of the cavities of the different cells. These corpuscles he suspected, but without sufficient grounds, to be the eggs of his polype. We find that, in a letter addressed to Bonnet, and quoted by this philosopher in his ' Considerations sur les Corps Organises, ' Trembley describes with great accuracy the statoblasts of a fresh-water vessel the current of blood was intermittent. Immediately on being emptied, the whole of the visible portion of the vessel contracted vigorously, and then slowly expanded for the reception of a fresh influx of blood, the pulses being at...