197 
I suppose that the eggs or more presumably — as I have 
never seen eggshells on the skin of the hirds — the larvæ are 
deposited by the fly on the birds. The larvæ subsequently ex- 
cavate a hole in the skin of the birds. Some larvæ have the 
anal end projecting from the tumor and on such larvæ are found 
distinet impressions corresponding to the border of the opening of 
the tumor 1 ). The hole, in which the parasite lies, is exeavated in 
the corium. The wall of the tumor (Fig. 3) is very thin ; the average 
Fig. 2. Two nestlings of Mimus modulator. R. H. Stamm phot. 
thickness being 0,2 mm, only the border of the opening is some- 
what thicker, measuring about 0,4 mm. The border is formed by 
a coarse layer of strongly compressed and shrivelled cells (a), which 
also continues a little along the inner side of the wall. The outer 
side of the wall is lined by an epithelium (b) which becomes rather 
thick near the opening, whereas it is thinner towards the base of 
the tumor. Under the epithelium is found a layer of connective 
tissue (c) enclosing some little biood vessels; the tissue is infil- 
trated with a great number of leucocytes, which are especially 
J ) In fig. 2 some larvæ are seen protruding ruuch more, f. i. on the heads; 
this is due to the preservation. 
