426 



SCIENCE 



[N. S. Vol. XXVI. No. 666 



II 



The spermatozoon produces two kinds of 

 effects upon the egg. It causes the egg to 

 develop and it transmits the paternal quali- 

 ties to the offspring. "We are here con- 

 cerned only with the developmental effects 

 of the spermatozoon. If the question be 

 raised as to what is the most obvious chem- 

 ical reaction which the spermatozoon causes 

 in the egg, the answer must be, an enormous 

 synthesis of chromatin or nuclear material 

 from constituents of the cytoplasm. After 

 the entrance of the spermatozoon the egg 

 has one nucleus which during segmenta- 

 tion is successively divided into two, four, 

 eight, sixteen, etc., nuclei. Boveri has 

 shown that each new nucleus has the same 

 size as the first nucleus after fertilization. 

 It is therefore obvious that one, and, to all 

 appearances, the foremost chemical effect 

 of the spermatozoon upon the egg is an 

 enormous synthesis of nuclear matter, and 

 to this we must give our attention. 



The main mass of the nucleus consists 

 of a salt, the acid of which is nucleic acid, 

 the base a protein substance of the type 

 of protamins, the synthesis of which has 

 been accomplished by A. E. Taylor, or 

 histones. The skeleton of the nucleic 

 acid molecule seems to be phosphoric 

 acid, to which are coupled at least 

 two chemical groups, namely, pui-in bases 

 (adenin, guanin and possibly other repre- 

 sentatives of the same group) and carbo- 

 hydrates—a pentose and a hexose. The 

 constitution of the nucleic acid may be 

 represented by the following diagram by 

 Burian, of which he states, however, that 

 it can not be entirely correct since it has 

 forty-one instead of forty atoms of carbon 

 in the molecule. 



From where does the material for this 

 synthesis of nucleic acid after fertilization 

 come? Our attention is first called to the 

 phosphoric acid. In the case of eggs de- 

 veloping in sea-water, one might think of 

 the possibility that these phosphates are 

 taken from the sea-water. I have made ex- 

 periments with artificial sea-water from 

 chemically pure salts which contained no 

 phosphates. Eggs of the sea-urchin ac- 

 complish their nuclein synthesis just as fast 

 in solutions free from phosphates as in 

 sea-water. Since the same is true for eggs 

 caused to develop by chemical methods, it 

 is obvious that the phosphates for the syn- 

 thesis of nucleins are derived from the 

 egg itself. The same is true for the other 

 constitutents of the nucleus, since the seg- 

 mentation of the egg of the sea-urchin can 

 proceed to the blastula and gastrula stage 

 in a solution containing only the chlorides 

 of sodium, potassium, calcium and mag- 

 nesium. 



Miescher found that the amoimt of 

 lecithin in the blood of the salmon is in- 

 creased during the period of the formation 

 of sex cells, and he concluded that lecithin 

 is one of the substances from which nucleic 

 acid is formed. The egg itself does not 

 seem to contain any preformed nucleic 

 acid, according to the investigation of 

 Kossel, in the hen's egg, and of Tichomiroff 

 in the eggs of insects. All eggs and pos- 

 sibly all embryonic cells possess compara- 

 tively large quantities of lecithin, a fact to 

 which Hoppe Seyler has already called 

 attention . • 



The lecithin consists of two different 

 groups of bodies, one being distearyl (or 

 oleyl), glycero-phosphoric acid, the other 

 being cholin. 



Thymin-Hexose — O- 



Pentose 

 Adenin 



O P P-0 



/ \/ \ 



HO OH HO OH 



./ \o/ 



,0s^ /O— Hexose — (Cytosin) 

 P P—0— Pentose 



-Guanin 



