64 INTERNAL STRUCTURE OF HEAD AND PROBOSCIS 



pair of pores. Kraepelin, in his description of the proboscis of the 

 blow-fly, described the labial glands and their ducts (but not their 

 histology) of that insect, his descriptions being similar to the con- 

 dition I find in M. domestica. Lowne, however, states that in the 

 blow-fly he traced the ducts of the gland cells through the oral 

 lobes to the apertures of the gustatory papillae, which he regarded 

 therefore as the apertures of the labial salivary glands. Graham- 

 Smith (1911) figures what he calls the "salivary gland of the oral 

 disc" but does not refer to its structure or relations in his paper on 

 the proboscis of the blow-fly. 



The appearance of the labial salivary glands of 31. domestica 

 calls to mind the maxillary glands of the ant Myrmica levinodis 

 which Janet has described and figured. The secretion of the 

 labial salivary glands serves, I believe, to keep the surface of the 

 oral lobes moist. 



