ANIMAL ORGANIZATION. 



100 



with another cavity (c), containing an unctuous 

 matter. During the formation of the quill this 

 unctuous matter is supplied through that channel, 

 and probably enters as an ingredient in its compo- 

 sition. The capsule of the pulp consists of two 



membranes, the one enveloping the other 



Fig. 36 



shows the bulb laid open by dividing the membranes 

 and turning them aside. The horny portion of the 

 quill is secreted by the internal membrane (i), and 

 deposited in successive laminse. The external 

 membrane is seen at o. The pulp itself, seen at 

 p, is still more curiously organized ; its surface 

 being fluted, or formed into longitudinal processes. 

 The horny matter, being deposited on these pro- 

 cesses, is moulded to their shape, and concretes 

 into laminse which converge from the circumference 

 of the cylinder towards the centre. The section 

 (Fig. 34) shows these converging laminae, which, 

 being of a dark colour, give to the surface of the 

 quill the appearance of being grooved ; this, how- 

 ever, is merely an optical illusion, occasioned by 

 the dark laminge being seen through the transparent 



