An Instance of Mutation. 137 



came to the conclusion that Lecanium (Coccus) viride varies 

 strongly. On the same locality and the same garden and 

 the same kind of Coffee (but different trees) one may 

 distinguish the following forms — 



"1. A large form with a very flat body, which is of a 

 clear green colour. 



" 2. A smaller form with a more elevated body, which is 

 less acuminate in front and of a darker dirty greenish 

 colour. Between these extremes there exist all kinds of 

 nuances." 



The following are the descriptions of the two forms 

 referred to in Prof. Keuchenius's letter. 



The Round Form. (Plate VI, fig. 1.) 



The margin nearly circular. The marginal .setae stout and frayed. 

 The skeleton is thick. The dermal cells large, irregularly oval 

 towards the margin, approximate, and smaller and more circular 

 towards the centre. Body elevated to give a more or less elevati d 

 shape. Colour dull brown to dull yellow. The loop more or less 

 inconspicuous. Dorsum thrown into minute transverse folds. 

 .Antennae very variable in number and relative length of segments, 

 the more usual number eight. Measurements : — 



Length/Breadth : :: 2*2, ■', 2-5, 3 2-25, 2*6 L75, 2-5 L"75, 2-5 1*75, 

 325 1-75, 3-25/2, :; 2. :; 2, 3 2. 3 2, 3 2, :: 2. 2-5, L-6, 325 2. 3-25 2, 

 :\-2r, 2. :i-2^2, 2-6 L-75, 2-25/2, 3/1-75, 3*25 I -To. 2-25 L'75, :; 1*75, 

 3/2, 2-25/2, 2-5/1 -5, 3/1 75, 3, 2. 2 L-75, 2-6/2, 25 I -75, 3 2. 3 2 mm. 



The Flat Oral Form. (Plate VI, fig. 2.) 



Oval, Hat, anterior extremity subacuminate. The marginal setae 

 less strongly developed hut of the same shape as the round form. 

 The loop more or less conspicuous. The chitinous skeleton thinner, 

 and the dermal cells round, fewer, scattered and not approximate. 

 Colour varies from greenish-yellow to greenish-blue. Dorsum not 

 thrown into folds. Antennae more usually eight-segmented, but 

 very variable in number and relative length of segments. 



Measurements : — 



Length Breadth : 4/2, 4 L 75, 4 2. Mi 2. 35 2, 3'55 2,3 25 2. I 2. 

 4 2. 4 2-20. :\ L-75, 3'5 2. I 2. :; I -To. 2"75 L'75, 3 2. 2-75 L'75, 3 2. 

 2-7.1 2, 2-71 1-71. 3-20 2. 3'5 2. 3*25 2. 3'5 2-25, 275 I 7:.. I 2, 3/2, 

 3*25 2, 35, 2. 3, 2. 3 1-75, 3 2.1 225, :: 2. 35 2, 2-75/1-7, 4/2 mm. 



