Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . thebranchial sacs. After floatingfor a certain time, each indi-vidual, as Dr. Chamisso firstdiscovered, propagates a youngone like itself. The solitarySalpa propagated by each in-dividual of the chain, is theproduct of an impregnated ovum, and is, for a time, suspended by a pe-duncle from the dorsal wall of the visceral cavity of the parent. In theSalpa zonaria, however, as many as three of such pedunculated younghave been found in one parent. When liberated, the solita
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . thebranchial sacs. After floatingfor a certain time, each indi-vidual, as Dr. Chamisso firstdiscovered, propagates a youngone like itself. The solitarySalpa propagated by each in-dividual of the chain, is theproduct of an impregnated ovum, and is, for a time, suspended by a pe-duncle from the dorsal wall of the visceral cavity of the parent. In theSalpa zonaria, however, as many as three of such pedunculated younghave been found in one parent. When liberated, the solitary Salpagrows to the size of the grand-parent, and then brings forth a social chainof young Salpoe, which, by the exercise of their uniparous generation,again give origin to the solitary and multiparous individuals. Thus, ob-serves Chamisso, only the alternate generations resemble each case is strictly analogous to the generation of the compoundAscidians, of which the solitary young gives origin, by gemmation, toa connected group, each individual of which again procreates, byimpregnated ova, free Aggregated young of Salpa zonaria. BRACHIOrODA. 48o BRACHIOPODA. The Brachiopods, like the Ascidians, are deprived of the power oflocomotion, and are attached by their shell or by a peduncle toforeign bodies. Their muscular tunic or mantle is, as it were, slitopen, and consists of two broad membranous expansions, called pal-lial lobes, which are covered by, and closely adhere to, two cal-careous plates, adapted to enclose and defend all the soft parts of theanimal. The branchial sac may be supposed to be equally cleft andadherent to the muscular one, so as to form the internal vascularlayer of the pallial lobe. The Brachiopods have left their testaceous remains in the mostancient deposits known to contain evidence of animal life : they flou-rished during the palaeozoic and secondary periods, and are mostabundant, and exemplified by the most varied forms, in the
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
