. Chemische Embryologie. Embryologie. SECT. 5] IN DER ONTOGENESE 801., dass die Dichte von Wasser in dem Arbacia punctulata Eier für einige Zeit gestanden hatte (ich Stunde) war immer niedriger als die von normalen Meerwasser (i -0229-i-02 i9). Dies führte ihn zu fragen, ob die Eier oder die Gelees alle anorganischen Material aus dem entnommenen Wassers hatte, und in der Tat Versuche zeigten, dass es immer ein Defizit von 2 bis 7 Zehntel Milligramm pro Kubikmeter Zenti- meter von Chlor in das Ei - Wasser nach einer Stunde, wenn ich Teil der Eier wurden in von 7 bis 10 Teilen Wasser ausgesetzt. Die Absorption

• Bildanbieter: Library Book Collection / Alamy Stock Foto
• Bild-ID: RJ8JMX
• Dateigröße: 7,2 MB (147,6 KB Komprimierter Download)
• Freigaben (Releases): Model - nein | Eigentum - nein
• Format: 2136 x 1170 px | 36,2 x 19,8 cm | 14,2 x 7,8 inches | 150dpi

Weitere Informationen

Dieses Bild ist ein gemeinfreies Bild. Dies bedeutet, dass entweder das Urheberrecht dafür abgelaufen ist oder der Inhaber des Bildes auf sein Urheberrecht verzichtet hat. Alamy berechnet Ihnen eine Gebühr für den Zugriff auf die hochauflösende Kopie des Bildes.

Dieses Bild kann kleinere Mängel aufweisen, da es sich um ein historisches Bild oder ein Reportagebild handel

. Chemical embryology. Embryology. SECT. 5] IN ONTOGENESIS 801. that the specific gravity of sea water in which Arbacia punctulata eggs had been standing for some time (i hour) was always lower than that of ordinary sea water (i-0229-i-02i9). This led him to ask whether the eggs or the jellies had abstracted any inorganic material from the water, and in fact experiments showed that there was always a deficit of from 2 to 7 tenths of a milligramme per cubic centi- metre of chlorine in the egg- water after an hour when i part of eggs were suspended in from 7 to 10 parts of water. The absorption was real, for eggs which had taken up all the chlorine that they would in one vessel took up no more when transferred to another; therefore the phenomenon was not due to an interference with the silver nitrate titration on the part of any egg-secretion. Eggs from which the jelHes had been removed did not show this behaviour, and, as histo-chemically the jelly was found to be rich in chlorine, everything pointed to the jelly being responsible (see Fig. 188). Most of what we know about the osmotic pressure of the egg- contents in echinoderms has to be deduced from what has been found to happen as regards the permeability of their membranes. McClendon in 191 o studied the electrical conductivity of masses of eggs before and after their fertilisation [Toxopneustes variegatus and Tripneustes esculentus) in a specially devised conductivity vessel. The following typical figures were obtained: Fig. Conductivity Unfertilised Fertilised .. 0-01182 0-01537 0-01153 0-01277 There was undoubtedly an increase of electrical conductivity at the beginning of development. This might have been due {a) to in- creasing permeability of the egg-membranes, {b) diminution of fatty phase of the ^gg, [c] dissociation of protein-electrolyte complexes. The second of these possibilities was quickly ruled out by centri- fugation experiments, which showed that just as much fat and oily matter was present after

Stockbilder mithilfe von Tags suchen

• bookcentury1900
• bookpublishernewyorkthem
• booksubjectembryology