GLAND STRUCTURES. 77 



and of the uniform diameter of from -s-trrin. to 



ioo" • w 1000 "•> 

 surrounded through its length, which is fully once 



and a half that of the entire body of the bee, by 

 between iooo and 1200 berry-shaped bodies, called 

 acini, of which one is much enlarged, B, Fig. 16. 

 In these acini the secretion is produced by cells, which 

 develop, perform their function, and pass away, to 

 be succeeded by others. The cells forming each acinus 

 are surrounded by a bag-like membrane, or propria, 

 through which the blood passes continually, to supply 

 the material out of which the secretion is elaborated. 

 System No. 1 is intracellular in type — i.e., every 

 part of the surface of each cell is absorbent, so that 

 the secretion it furnishes has to be removed from its 

 interior by a duct, which enters its wall, becomes sur- 

 prisingly delicate, and takes within a lengthened, 

 sinuous course, bringing itself in contact with the 

 cell plasma. These chitinous tubes, each about 

 T¥FoU m - * n diameter, after leaving the cells, pass 

 parallelly through an enveloping tube (st, B), towards 

 d, where, by independent perforations, they enter 

 the main duct, which at this point raises itself into a 

 sort of papilla, having a sieve-like end. In the red 

 ant, a similar gland (K, Plate VII.) has its cells free, 

 the propria being wanting. Its form as given should 

 be studied. Tracing this duct onwards towards the 

 mouth, we find it enter a pouch, or ampulla, lying 

 at the side of, and beneath, a plate which forms 

 what may be termed the mouth-floor (Fig- 17). 

 The part (pi) of this plate drops as a flap towards, 

 and joins, the upper extension of the tongue, so 

 that food passing over the latter can be uninter- 



