'28O ANOMALIES OF DEVELOPEMENT. CHAP. V. 



round the egg and is there accumulated and con- 

 verted into a sort of spongy lump which vegetates 

 and augments till it forms what is called a gall. 

 The gall thus formed affords both shelter and nou- 

 rishment to the young maggot, which after being 

 converted into a fly pierces its enclosure and launches 

 into the open air. 



Oakap- The most remarkable of such galls are those 

 produced on the Oak-tree, and known in this 

 country by the vulgar name of Oak-apples ; of the 

 origin and growth of which I think Malpighi gives 

 a detailed account, but of which I cannot now 

 offer any abstract to the reader, not being at present 

 furnished with a copy of his works. The following 

 are some observations which may in the mean time 

 serve as a substitute. About the end of May, 1808, 

 having observed upon an Oak-tree some of the galls 

 in question (PL IX. Fig. 8.) I had some of them 

 gathered for the purpose of examination. The 

 largest was then about the size of a Golden Pippin, 

 soft and spongy to the touch, and covered with a 

 fine and glossy epidermis of a white colour, but 

 changing in some places to red, and hence not 

 much belying in appearance its vulgar name. At 

 its base it was furnished with a number of scales 

 or leaves resembling a calyx, which proved upon 

 examination to be the outer scales of the original 

 bud. On cutting the gall open whether by a lon- 

 gitudinal or transverse section, a number of oval 

 or cylindrical bodies of a whitish colour were found 

 2 



