ABSTRACT
The disappearance or the decrease in level of proteins during development generally can be considered as a nutritional process, since no free or bound nitrogen leaves the cell during echinoid development. An interesting aspect of the proposed derivation of the yolk platelets from the Golgi vesicles is the possibility that the accumulation of nutritional matter would occur within a lysosome: the lysosomes are, of course, of Golgi derivation. The observation that the yolk components of eggs of other organisms are progressively degraded and the degradation products re-utilized as food by the developing embryos applies to echinoids mostly by analogy. Nevertheless some proof of yolk lysis exists, but for the most part no direct evidence has been presented that the nutritional molecules, whose degradation has been demonstrated, were originally stored in the yolk platelets, or elsewhere. The general lack of precise information about the origin and the chemical nature of the yolk in echinoderms leads to uncertainty yolk utilization.
