98 PARTHENOGENESIS 



fecundated silk-worm moths changed in a few days in the well- 

 known manner, their sulphur-yellow colour gradually becoming 

 converted into dark yellow, then into orange, red, violet, and lastly 

 into bluish or slaty-grey, which had often taken place even on the 

 third day after laying. The eggs at the same time remained 

 tense, and bore in their middle the flat impression which is also 

 well known. In this bluish colour, as the token of their vitality, 

 I got these eggs through the winter, and in the following spring 

 they furnished me with a great number of caterpillars. I must 

 here observe, that the previously mentioned change of colour of the 

 Silk- worm's egg does not arise from a commencement of the deve- 

 lopment of the embryo, but is only the consequence of a peculiar 

 alteration of the yelk, which at first shines through the colour- 

 less, dimly transparent egg-shell with a sulphur-yellow colour, 

 and subsequently with the various changes of colour. A few of 

 the eggs laid by the fecundated moths retained their sulphur- 

 yellow colour, and at last shrivelled up. These certainly lost 

 their vitality, because from some cause the penetration of seminal 

 filaments into the micropyle was prevented, and thus the fecun- 

 dation of these eggs was not attained*. 



To the eggs obtained from the seven virgin silk-worm moths I 

 directed particular attention from the first, as I was very curious 

 to see whether a Parthenogenesis would not be observable at 

 least in some individuals of these eggs. I was therefore much 

 surprised when I perceived exactly the same well-known change 

 of colour which took place in the fertilized eggs soon after their 

 deposition, in a far greater number of these eggs than I could 

 have hoped, but in the unfecundated eggs it occurred much 

 later and more slowly. From some of these virgin silk-worm 

 moths I had obtained thirty to forty, from others only about ten 

 to twenty eggs, the colour of which slowly altered in comparison 

 with the other eggs which had remained yellow, and which gra- 

 dually shrivelled up. But this change of colour did not go on 

 quite constantly in the same way as in the fertilized eggs. Only 

 a few unfertilized eggs passed through the entire alteration of 

 colour to the slate-grey ; most of them remained stationary at 

 earlier steps of the change, only became reddish or violet, and 

 even shrivelled up at last like the pale yellow unfertilized eggs, 



[* This is an insufficient cause, from Siebold's own showing. W. S. D.] 



