28 GENERATION OF INSECTS 



escaped from a small aperture in the closed box, and I 

 was unable to discover their hiding place. Being curious, 

 therefore, to know their fate, I again prepared three of 

 the same snakes, which in three days were covered with 

 small worms. These increased daily in number and size, 

 remaining alike in form, though not in color. Of these, 

 the largest were white outside, and the smallest ones, 

 pink. When the meat was all consumed, the worms ea- 

 gerly sought an exit, but I had closed every aperture. On 

 the nineteenth day of the same month some of the worms 

 ceased all movements, as if they were asleep, and ap- 

 peared to shrink and gradually to assume a shape like an 

 egg. On the twentieth day all the worms had assumed 

 the egg shape, and had taken on a golden white color, 

 turning to red, which in some darkened, becoming almost 

 black. At this point the red, as well as the black ones, 

 changed from soft to hard, resembling somewhat those 

 chrysalides formed by caterpillars, silkworms, and similar 

 insects. My curiosity being thus aroused, I noticed that 

 there was some difference in shape between the red and 

 the black eggs [pupae], ^ though it was clear that all were 

 formed alike of many rings joined together; neverthe- 

 less, these rings were more sharply outlined, and more 

 apparent in the black than in the red, which last were 

 almost smooth and without a slight depression at one end, 

 like that in a lemon picked from its stalk, which further 

 distinguished the black egg-like balls. I placed these 

 balls separately in glass vessels, well covered with paper, 

 and at the end of eight days, every shell of the red balls 

 was broken, and from each came forth a fly of gray 



1 Throughout this work Redi uses the word " uova " where the 

 context shows that pupa is meant. In this he followed Harvey, 

 who called any embryonic mass an " egg." 



