Abstract— The changes in phospholipids and gangliosides during ontogenesis of chick retina have been compared with those in brain. Three phases of accumulation of ganglioside NeuNAc in the retina were detected. In contrast, brain NeuNAc rapidly increased during embryonic life until hatching, followed by a slower increase up to the adult stage. The phospholipid changes in retina and in brain occur in a‐similar manner to the variations observed for gangliosides, however in retina the changes of phospholipid content are less marked than in brain, during embryonic life. There were marked changes in the retina and brain ganglioside patterns with age. Gd3 and Gd1b decreased rapidly in per cent; correspondingly, Gd1a increased during embryonic life and became the major ganglioside in place of Gd3. There was a similarity between ganglioside patterns of chick retina and brain. Except for some slight variations during embryonic life, the retinal phospholipid pattern did not change noticeably.

THE study of the evolution of free nucleotides in the central nervous system (CNS) during post-natal development has not been exhaustive so far. MANDEL, BIETH and WEILL (1957) investigated the adenylic nucleotides by the classical technique of LEPAGE (1949), COHEN and LIN (1962) studied the ATP by column chromatography and enzymic determination, and DEW, MUKUNDAN, SRIVASTAVA and S u m , (1963) analysed the total acid-soluble nucleotides by U.V. absorption. To explore more precisely the evolution of free nucleotides in the CNS during development, we used the technique of separation by column chromatography followed by paper chromatography. MATERIAL A N D METHODSThe experiments were conducted on albino rats of a homogenous strain, Wistar, reared in our laboratory. For each experiment we took groups of twenty rats of 1 day of age; eighteen rats of 2 days; eleven-thirteen rats of 7 days; nine rats of 14 days; seven rats of 21 days; seven rats of 28 days and five rats 35-days-old and adults older than 35 days. The young rats were sacrificed by immersion of the whole animal in liquid nitrogen. The adults were decapitated and the head was immediately put into liquid nitrogen. The brains were taken out in the frozen state and pooled in the liquid nitrogen until they were weighed. The extraction, separation and quantitative estimation of free nucleotides was done by the technique already published by us (MANDEL and HARTH, 1961).

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