Archive image from page 370 of The anatomy, physiology, morphology and. The anatomy, physiology, morphology and development of the blow-fly (Calliphora erythrocephala.) A study in the comparative anatomy and morphology of insects; with plates and illustrations executed directly from the drawings of the author; CUbiodiversity4765349-9875 Year: 1890 ( THE DEVELOPMENT OF THE DORSAL VESSEL 657 Jaworowski, however, says that the dorsal vessel in the newly-hatched larva of Chironomus ' consists of two lateral halves, in which every nucleus indicates a muscle-cell. Each muscle-ring, which is gradual
Archive image from page 370 of The anatomy, physiology, morphology and. The anatomy, physiology, morphology and development of the blow-fly (Calliphora erythrocephala.) A study in the comparative anatomy and morphology of insects; with plates and illustrations executed directly from the drawings of the author; CUbiodiversity4765349-9875 Year: 1890 ( THE DEVELOPMENT OF THE DORSAL VESSEL 657 Jaworowski, however, says that the dorsal vessel in the newly-hatched larva of Chironomus ' consists of two lateral halves, in which every nucleus indicates a muscle-cell. Each muscle-ring, which is gradually differentiated from a pair of cells, therefore consists of two lateral halves. For a long time both the cells and the enclosed muscle-fibres are seen.' He further states that ' the valves are developed from the same muscle- cells.' From the manner in which the nuclei are arranged in the dorsal vessel, I think there can be no doubt it is at first a tube formed by two lateral rows of cells. Sections show that in the Fk;. 89.—A transverse section through the pericardium and dorsal vessel of a Blow- fly nymph just before its escape from the pupa case, ai, cuticular layer of the abdominal integument; /, fat bodies; g, ganglion cells; /;, hypodcrmis ; m, muscular coat of the dorsal vessel ; /, pericardial septum ; ps, pericardial sinus; s, blood sinus opening into pericardial sinus ; /;-, Ir, tracheal vessels. pupa of the Blow-fly, the fibrillae which surround the dorsal vessel are gradually differentiated from the cell substance of large cells, which surround the lumen of the tube. The nuclei of these cells are very large, and project into the interior of the tube. As to the origin of the muscle-cells, either in the embryo or pupa, nothing is certainly known ; but so far as is known, the manner in which the dorsal vessel originates is in favour of VVeismann's view that it is a hollow muscular tube, and not a complex organ consisting of connective and muscular tissue. For fur
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