CHAIRMAN S INTRODUCTION 47 1 



The vectors of Fig. 3 may primarily represent pathways of protein 

 synthesis. As experiments with labelled precursors show, incorporation of 

 for example ['^C]-leucine into proteins runs parallel with the incorporation 

 of [^^C]-adenine into ribonucleic acid, cf. Markman [18]. It is evident that 

 the ribonucleic acid plays the same fundamental role in protein synthesis 

 in the sea urchin material as elsewhere. As far as it is possible to resolve 

 the sites of incorporation, that of the ribonucleic acid precursor (e.g. [^^C]- 

 adenine) occurs primarilv in the nuclei. It seems thus probable that the 

 synthesis of ribonucleic acid on which the protein svnthesis is dependent 

 occurs in the nucleus. I trust that the question about the site of ribonucleic 

 acid formation will be more deeply discussed in the paper by Dr. Prescott 

 who refers to another material, viz. amoebae. 



ft 



An Veg 



AP>^ 



•-VP 



Fig. 4. Diagram of the vegetal and animal vectors over the whole embryo, 

 VP vegetal pole, AP animal pole. Vectors representing the opposite synthetic 

 pathways on the same embryonic level form the same angle with the vegetal- 

 animal axis VP-AP. 



In this context anabolic processes other than ribonucleic acid and 

 protein synthesis must be disregarded. It may only be noticed in passing 

 that my colleague Immers found also indications of a parallelism between 

 incorporation of amino acids into proteins and an incorporation of ["^'S]- 

 sulphate into mucopolysaccharides. 



Figure 4 gives a diagram of the vegetal and the animal \ectors of 

 ribonucleic acid and protein synthesis over the whole embryo from the 

 vegetal (VP) to the animal pole (AP). The levels in the embryo are given 

 by the angles that the vectors form with the baseline (AP-VP). There is 

 no need to emphasize how grossly simplified this picture is. Nevertheless 

 it may be of some use. Different kinds of ribonucleic acids must be formed 

 in the nuclei where they presumably receive their " information" from the 

 deoxyribonucleic acid, cf. discussion in [3]. 



As indicated in Fig. t,{(i), certain pathways of synthesis may be inde- 

 pendent of the level in the animal vegetal system. In Fig. 4 emphasis is 



