94 PARTHENOGENESIS 



changes which the silk- worm eggs rendered capable of deve- 

 lopment by a fertile copulation undergo with regard to their 

 outline, colour and contents, from the moment of deposition up 

 to that condition in which they remain more or less unaltered 

 through the whole winter. He also points out particularly that 

 the coloured membrane which makes its appearance below the 

 egg-shell, and which passes through a definite change of colour, 

 upon which the changes of colour of the whole egg depend, 

 is certainly in general a sure indication that fecundation has 

 taken place, but especially the most certain token that the eggs 

 are actually capable of development. Herold at the same time 

 figures an embryo * as it occurs in the middle of winter in the 

 fecundated egg of a silk-worm moth, after the egg has completed 

 its change of colour within the first eight or ten days after depo- 

 sition. On the seventh plate Herold represents the consecutive 

 changes " in regard to outline, colour and contents undergone, 

 in the first weeks after deposition, up to the state in which 

 they remain more or less unaltered throughout the winter, by 

 many of the eggs which the female silk- worm moth lays by her- 

 self, without copulation with the male, and many of which are 

 nevertheless endowed in different degrees with the power of de- 

 velopment almost like those which are actually rendered fertile 

 by the assistance of the male." He could distinguish various 

 degrees of the faculty of development of unfertilized eggs, which 

 manifested themselves by infinite differences in the disposition, 

 number, form, and strength of colour, of the coloured parts of 

 the egg. In some of these unfecundated eggs the faculty of 

 development had attained such a high degree, that Herold was 

 able to extract a foetus from one of them in the middle of winterf. 

 According to Herold's further statements, however, embryos 

 were not found in all unfertilized eggs capable of development 

 which he examined in the winter, and he had also never seen 

 young caterpillars creep out of unfertilized eggs, as they had 

 previously ceased to live. 



Moreover, Malpighi was already acquainted with the distinc- 

 tion between fertilized and unfertilized silk-worm eggs. This 

 distinguished naturalist long since knew, what has been left un- 



* hoc. cit. sup. tab. 6. fig. 15. t hoc. cit. tab. 7- fig- 19. 



