THE LIFE-HISTOUY OF A I-EI'tDOPtKROUS INSECT. 291 



mules. He then goes into detail and shows vvlial propurtion of female 

 moths give fertile eggs parthenogenetically, and states that in his " re- 

 seai'ehes into the subject of sericulture in the Soutli as well as in Piedmont 

 and Lombardy, the same remarks have often been heard." He adds: — 

 " Although we do not attach a great belief in this singular phenomenon 

 among animals so highly organised as butterflies, iu the face of all 

 these affirmations and of some doubts it became necessary to 

 submit the fact to experiment." ]n 1850 some partial experiments, 

 which gave no certain results, were made, the experiments not ha\ang 

 l)een followed up to the hatching of the eggs considered to be fertile. 

 In 1851, further experiments were made on yellow cocoons from Briance 

 or Milan, of a form which gives only one generation per year ; the ex- 

 periments were surrounded by every possible precaution, and wei-e made 

 on a large scale. A summary of the results is then appended. 



The first experiment was as follows :— In June 1851, three Imndred 

 cocoons were selected, and, so that there should be no communication 

 between the imagines on their emergence, each cocoon was placed in a 

 small cardboard box carefully covered with gauze, which completely im- 

 prisoned the moth on its emergence. These three hundred cocoons 

 produced 147 females and 151 males. The boxes containing the males 

 were removed, and those containing the females were carefully pre- 

 served without being uncovered. 



Of the 147 females, fi only gave, in the course of their laying, really 

 fertile eggs. 2 of these gave seven, 2 four, 1 Ave, and 1 two. These 

 29 eggs, preserved in their respective boxes without Ijeing uncovered, to 

 render error im2)0ssible, were the only ones which hatched in May 1852. 

 There were also a large number of other eggs, which })assed from the 

 pale yellow (which is their colour when newly laid) to the more or 

 less slaty-grey Avhich replaces it after some days in fertile eggs ; but at 

 length these eggs, Avdiich gave at first the characteristic sign of fecundity, 

 shrivelled up, whilst a few others, which preserved until spring the 

 usual form and colour of fertile eggs, did not produce larvte ; on opening 

 these last eggs they were found to contain putrefied matter, apparently 

 recently formed. 



In this experiment, therefore, based on the eggs of 147 females, only 

 29 larvje were produced. The total number of eggs was about 58,000, 

 so that the completely formed eggs were about in the proi)ortion of 

 1 : 2,000. 



In Juh'^ of the same year (1851), a second experiment was made on 

 white cocoons coming from South China, of a form giving five or six suc- 

 cessive generations in one year. Fifty cocoons were shut up as in the 

 last experiment, and from these emerged 23 females and 26 males. 

 Seventeen of the twenty- three females gave completel}' fertile eggs. 

 These fertile eggs were in the proportion of 1 in 17, and hatched 17 

 days after being laid. One of these females gave 113, and the least 

 productive gave 12. The total number of eggs laid by these 23 females 

 was 9,000, of Avhich 520 pi'oduced caterpillars. 



The conclusions arrived at by Mr. Jourdan {I.e., p. 1095) are very 

 interesting. The experiments proved conclusively that virgin females 

 of the silkworm moth could reproduce their kind without copulation 

 with males. Tliis pai'thenogenetic reproductive power Avas, however, 

 exceedingly feeble, as the figures (quoted prove. Again, of the two 



