28 Cutler, Parthenogenesis in Animals 



very numerous, but whatever may be ; the colour of the parent all 

 the parthenogeneticalry produced offspring were alike in having 

 a pattern of green and brown. 11; (is as growth proceeds thatJ 

 the different colour characteristics of the adults are gradually 

 produced. Also there was no evidence, as regards green or 

 brown, that the colour of the mother had any influence on the 

 proportion of the young which finally assumed these hues. 



Artificial Parthenogenesis. 



The second part of the paper deals with the remarkable ex- 

 periments which have been performed on the eggs of various 

 animals, not normally parthenogenetic, causing them to develop 

 without the action of the spermatozoon. This phenomenon has 

 been termed artificial or experimental parthenogenesis. I do 

 not intend to give more than a very, general outline of the work 

 which has been done, as the subject is fully treated in Loeb's 

 book, "Artificial Parthenogenesis," and also in that of Delarge 

 and Goldsmith, " La parthenogenese naturelle et experimentale." 

 Though artificial parthenogenesis has only assumed a prominent 

 place in biological literature during the last few years, the pheno- 

 menon was noted by a few observers much earlier. 



Boursier in 1847 stated that a virgin silkworm placed in sun- 

 light and then in shade had produced eggs from! which cater- 

 pillars had developed. 



Tichomoroff in 1886 published a short note on the artificial 

 parthenogenesis in insects, in which he described how he had 

 obtained caterpillars from a few unfertilised eggs (6 out of 99) 

 of the silkworm by rubbing them between two> pieces of cloth. 

 This experiment is open to doubt, as later work has demonstrated 

 that a small proportion of unfertilised eggs of the silkworm will 

 develop without outside aid. In 1902 the same naturalist used as 

 the stimulating agent concentrated sulphuric acid with marked 

 success 



O. Hertwig, in 1890, by shaking the eggs of Astropecten and 

 Asterias induced the first stages of development, and in 1899 

 Loeb found that cleavage of unfertilised eggs of the sea urchin 

 Could be induced by the action of hypertonic sea-water. Since 

 this date the number of workers have been exceedingly numerous 

 and development has been induced by the most diverse means. 

 I shall therefore content myself wjith giving; a brief resume of 

 the most important theories that have been deduced from ex- 

 periments, together with a short account of some of the more 

 important experiments performed. 



