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SCIENCE 



[N. S. Vol. XXVII. No. 68.-; 



tains the same kind of nucleic acid as is 

 found in the nueleoproteins of many 

 somatic cells. Here, there is no noticeable 

 difference in chemical structure, but in the 

 protein part of the nucleoprotein the dif- 

 ference, as has been pointed out, is most 

 striking. Hence, it seems reasonable to 

 suppose that some special function attaches 

 to this peculiar structure of the protein 

 present in the nucleoprotein of the sperma- 

 tozoon nucleus, although it must be 

 granted that at present there are no facts 

 available to support any theory. 



We can not avoid attaching considerable 

 significance to this marked chemical dif- 

 ference in the composition of the cytoplasm 

 and karyoplasm of the sperm cell, any more 

 than we can overlook the striking pecul- 

 iarity of structure in this particular type 

 of cell, in which the nucleus completely 

 overshadows the cell body. We may well 

 ask why the cytoplasm, composed as it is 

 of a highly complicated mixture of differ- 

 ent materials, should be so dominated by 

 a nuclear substance composed almost en- 

 tirely of a nucleoprotein, the basic portion 

 of which is made up of the simplest type 

 of protein known, with its laxge percentage 

 of diamino acids? The egg cell, on the 

 other hand, is composed in large measure 

 of cytoplasm, and further, the nucleus of 

 this type of cell has a chemical structure 

 radically different from that of the karyo- 

 plasm of the spermatozoon, since such 

 nucleoprotein as it contains is widely vari- 

 ant in chemical make-up from the forms 

 present in the sperm nucleus. It is not 

 strange, therefore, that Miescher and 

 others for a time considered protamine 

 nucleate as the important factor in the 

 process of fertilization. Various lines of 

 experiment have apparently demonstrated, 

 however, that such is not the case ; still the 

 problem remains, and there must be some 

 explanation to account for these striking 

 chemical differences in the make-up of the 



karyoplasm in the two types of cells. The 

 chemist and the cytologist are alike unable 

 to find any adequate explanation for the 

 reactions that occur in the commingling of 

 sperm and germ cells. Extracts of various 

 kinds made from the spermatozoon, which 

 might take up some one or more chemical 

 substances as yet unrecognized, have been 

 so far inoperative in inducing fertilization. 

 There can be no question, however, that 

 many of the problems connected with fertil- 

 ization, cell division, heredity, etc., are 

 bound up in the chemical constitution of 

 the different components of the sperm and 

 germ cells. Chemical activity of some sort 

 is unquestionably incited by the sperm 

 cell, and we may well believe with Loeb^* 

 "that the direct and essential effect of the 

 spermatozoon and the methods of artificial 

 parthenogenesis is the starting of a definite 

 chemical process," although we are wholly 

 in the dark as to the exact nature of the 

 reactions involved. It might be con- 

 jectured that the spermatozoon serves to 

 introduce a positive catalyzer into the egg 

 cell and thereby starts or accelerates syn- 

 thetical processes by which the egg is made 

 to develop, with consequent transformation 

 of a portion of the cell protoplasm into the 

 specific nuclein or chromatin substance of 

 the nucleus. Experiment along these lines, 

 however, has failed to give any proof of a 

 positive catalyzer being carried into the 

 egg (Loeb). 



There may be legitimate differences of 

 opinion as to the relative importance of the 

 nucleic acid and of the protamine base ; 

 of their relative significance in the trans- 

 ference of racial and family character- 

 istics, for example. Loeb, however, has 

 said "that the nucleic acid is of more im- 

 portance for heredity than protamines and 

 histones. " This may be so, although the 

 evidence for such a view is not thoroughly 



"-" The Dynamics of Living Matter," 1906, p. 

 178. 



