Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . l phenomena of the reproductive gem-mules have been studied by Dr. Farre with much care and success inthe sponge-like Halodactylus (^Alcyo7iium gelatinosunij of Pallas).They appear in spring as minute whitish points just below the one of these points be carefully turned out with a needle, it is74 found to consist of a transparent sac, containing generally from four to six of the larvas. Theseare of a semi-oval form, with the margin of theirplain surface devel
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . l phenomena of the reproductive gem-mules have been studied by Dr. Farre with much care and success inthe sponge-like Halodactylus (^Alcyo7iium gelatinosunij of Pallas).They appear in spring as minute whitish points just below the one of these points be carefully turned out with a needle, it is74 found to consist of a transparent sac, containing generally from four to six of the larvas. Theseare of a semi-oval form, with the margin of theirplain surface developed into tubercles support-ing groups of vibratile cilia {fig. 74.).* Thebody presents a simple granular structure; thegemmule swims about actively by the vibrationof its cilia, the motion of which seems to beunder its control. They generally swim with Larva of Halodactylus, from ^, n t . i above; the cilia as when slowly the couvcx part lorwards ; somctimcs tliev acting round the margin in • , , . waves. Simply rotate upon their axis, or execute a series of summersets; or, selecting a fixed point, they whirl round. * The movements of the cilia, which give the appearance of a succession ofAvaves, have been closely analysed in XXXV. pp. 410, 411. BRYOZOA. 153 it in rapid circles, carrying every loose particle after them; orthey creep along the bottom of the watch glass upon one end witha waddling gait: but at the expiration of forty-eight hours theyattach themselves to the surface of the glass, and the rudimentsof the cell may be observed. In the Flustra carbesia the ova are developed between the cell andthe body of the polype, which yields to, and is destroyed by, them asthey are developed. They produce ovate, yellow, ciliated larvce,which, by virtue of the contractility of their tissue and the activevibration of their cilia, escape with their small end foremost fromthe opening of the cell. They then, after a short term of locomotivelife, settle and subside, the outline of t
Size: 1586px × 1575px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
