. Chemical embryology. Embryology. SECT. 5] IN ONTOGENESIS 797 The independence of the environment which has been noticed in fresh-water teleosts extends also to marine teleosts, where there is a sharp contrast as against elasmobranchs. Dakin obtained the fol- lowing values by direct freezing-point determinations: Sea water Egg-contents of Pleuronectes platessa Adult blood of Pleuronectes platessa Egg-contents of Scyllium canicula Adult blood of Scyllium canicula AH -1-91 -0-70 -0-75 -I-80 -I-go. Fig. 187. This was in agreement with Bottazzi's well-known findings that the osmotic pressure and
. Chemical embryology. Embryology. SECT. 5] IN ONTOGENESIS 797 The independence of the environment which has been noticed in fresh-water teleosts extends also to marine teleosts, where there is a sharp contrast as against elasmobranchs. Dakin obtained the fol- lowing values by direct freezing-point determinations: Sea water Egg-contents of Pleuronectes platessa Adult blood of Pleuronectes platessa Egg-contents of Scyllium canicula Adult blood of Scyllium canicula AH -1-91 -0-70 -0-75 -I-80 -I-go. Fig. 187. This was in agreement with Bottazzi's well-known findings that the osmotic pressure and salinity of teleostean blood was different from the sea (though it varied with it), while the osmotic pressure and sahnity of elasmobranch blood was the same as the sea. Death of the plaice egg destroyed its osmotic independence. Thus the teleost egg, floating in sea water of salinity 35 per cent., had an osmotic pressure corresponding to a salinity of only 14 per cent.; corre- spondingly it will develop perfectly well in a mixture of 80 per cent, fresh and 20 per cent, salt water. With regard to Scyllium eggs, Dakin. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Needham, Joseph, 1900-. New York: The MacMillan Co.
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