ANUBXDA. 367 



and the only difference between the sexes in Anurida is 

 that the females are, as a rule, somewhat larger and more 

 bulky than the males and, moreover, the ripe ovaries 

 usually show through the lesser pigmented cuticle on the 

 ventral side as a pair of yellow patches. By the latter 

 character the females can generally be recognised with a 

 hand lens. 



2. Integument and Colouration. 



The integument consists of (a) the chitinous cuticle, 

 (b) the hypodermis or chitogenous layer, and (c) a base- 

 ment membrane (vide Plate II. , figs. 16 and IT). 



The cuticle varies slightly in thickness in various 

 parts of the body, being thinner on the appendages than 

 elsewhere. It is quite colourless, and its surface is thickly 

 studded with minute, somewhat conical tubercles, which 

 are very evenly spaced apart (fig. 6). Over the apex of 

 the labium these tubercles are replaced by irregular 

 protuberances of the cuticle, but all transitions are 

 observable between the two (fig. 12 J. On the labrum the 

 tubercles are also modified, and they exhibit a tendency 

 to be arranged in horizontal rows (fig. 13). The 

 tubercles are absent from the inner aspect of the basal 

 half of each of the legs, and scattered over the abdomen 

 are numerous small areas from which they are likewise 

 wanting; these latter areas correspond with the positions 

 of insertion of the tergo-sternal and other muscles 

 (Plate VI., fig. 60). The cuticle, when viewed in very 

 thin sections, is seen to consist of two layers, the line of 

 separation between them passing just below the bases of 

 the tubercles. These layers are best differentiated in 

 preparations stained with Mann's methyl-blue-eosin, 

 when the inner stratum of the two stains a brilliant blue, 

 while the outer one has a stronger affinity for t lie 



