CONTRIBUTIONS FROM THE ZOÖLOGICAL LABORATORY OF 
THE MUSEUM OF COMPARATIVE ZOÖLOGY AT HARVARD 
COLLEGE. E. L. MARK, DiIRECTOR.— No. 160. 
NATURAL AND ARTIFICIAL PARTHENOGENESIS.! 
ALEXANDER PETRUNKÉVITCH. 

WrrH the discovery by Oscar Hertwig, in 1875, of the essen- 
tial nature of fertilization as the union of the nuclei of the two 
parental germ-cells, the line of research in the branches of biology 
dealing with reproduction became more clearly defined. While 
on the one hand this discovery put an end to all guess-work, on 
the other hand it threw light on the part taken in development 
and heredity by both egg and sperm. To this was added later 
the knowledge of the behavior of the centrosomes in fertilization, 
the whole bringing us nearer to an understanding of the other- 
wise incomprehensible phylogenetic separation of living beings 
into two sexes, impelled by the necessity of amphimyxis. 
Again, the theory of the individuality of the chromosomes and 
the study of the process of reproduction in maturation afforded 
us an insight, incomplete though it be, into those forms of 
reproduction which are not accompanied by fertilization. New 
questions were gradually evolved, but since they had their source 
in facts recognized by everyone, they were so precise, that when, 
five years ago, I entered upon the study of parthenogenesis 1n 
the honey-bee, I had before me a very definite problem. 
All this I purposely mention here. By the time I had pub- 
lished the first part of my research and had gone on in the 
Study of natural and artificial parthenogenesis, there began to 
appear objections not only to the results of my own work, but 
even to statements hitherto undisputed, as well as to the toe 
Sober interpretations of facts. These objections were raised 
! Read before Section F — Zodlogy — of the A. A. A. S. at the 54th annual 
méeting in Philadelphia, 1904. 
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