History OF ARTIFICIAL PARTHENOGENESIS 49 
the egg of the frog can be induced to develop parthenogeneti- 
cally by a puncture with a needle. It is not impossible that in 
the experiments mentioned here on silkworms also a rupture 
or puncture of the surface layer was the cause of the develop- 
ment. 
Tichomiroff’s researches caused Dewitz! to interpret as 
parthenogenesis a previous observation of his upon frog eggs. 
When I was working in the spring of 1885 under Professor Zuntz 
in the physiological institute of the agricultural college in Berlin, I 
placed, for certain reasons, unfertilized eggs of Rana fusca in a solution 
of corrosive sublimate. The next morning, to my astonishment, 
I found them swollen and segmented. In some of the eggs only one 
division had taken place, in others more than one; in some the cleavage 
was irregular, but in very many perfectly normal... . . Moreover, 
this occurred just as well if the eggs remained lying in the sublimate 
as also when they had remained there only a few minutes. ... . 
Hence it can be concluded that sublimate exerts a stimulus which causes 
the first division. 
There can be no doubt that the last conclusion is incorrect. 
What Dewitz observed was obviously a coagulation phenome- 
non which led to a wrinkling of the surface of the egg and in 
which the essence of cell division, viz., nuclear division, was 
absent. This was afterward pointed out by Roux.’ 
In the eighties and nineties, the attention of morphologists 
was directed to the finer processes of nuclear and cell division. 
This line of work yielded to the domain of facts in which we 
are interested here, the observation that the unfertilized eggs of 
certain sea-urchins may show the beginning of nuclear or even 
a cell division if they remain long enough in sea-water. The 
first systematic observation on this count probably originated 
from Richard Hertwig.’ 
1 J. Dewitz, ‘‘Kurze Notiz ueber die Furchung von Froscheiern in Sublimat- 
lo6sung,”’ Biol. Centralbl., VII, 93, 1888. 
2W. Roux, Gesammelte Abhandl., II, 432. 
3R. Hertwig, ‘‘Ueber die Entwicklung des unbefruchteten Seeigeleies,”’ 
Festschrift fiir Gegenbaur, Leipzig, 1896. (Hertwig had already reported on these 
observations in the German Zoological Association in 1892.) 
