166 ROUND THE YEAR 



Harvey had studied the scholastic philosophy too, 

 and he treats us to many pages of learned disquisition. 

 Thus he explains to us that there are two ways in 

 which things come into being. The material may be 

 ready to hand, and require only to be supplied with 

 form. The sculptor makes a statue, but he does not 

 make the marble. In other cases material as well as 

 form has to be supplied, or at least brought together, 

 as when a potter gathers clay, and adds bit to bit to 

 make an image. In some animals, Harvey goes on, 

 the material is all collected beforehand, and only 

 requires to be thrown into shape ; that is metamor- 

 phosis. In others the parts have to accrete substance 

 to themselves and grow ; that is epigenesis. Insects 

 are developed by metamorphosis, but the higher 

 animals, which have blood, develop by epigenesis. 



Such was the kind of speculation which was current 

 in the learned world when Malpighi and Swammerdam 

 began to explore the transformations of Insects with 

 the scalpel and the microscope. I do not know which 

 was the first to observe the fact, but Malpighi was the 

 first to announce that in a Lepidopterous larva nearly 

 ready for pupation the legs and wings of the imago 

 may already be distinguished by dissection. The 

 observation is to be found in that memorable treatise 

 on the Silkworm, which Malpighi wrote for our Royal 

 Society in 1668, and which they printed in the 

 following year. When the larva, he tells us, has spun 

 up, its skin splits, and the pupa emerges like a new 

 animal born of the old one. The antennae stand out 

 in the place formerly occupied by the mandibular 

 muscles. The legs of the Moth appear inside the 



