''310 Annals Entomological Society of America [Vol. XI, 



The HisTOL()(riCx\L Structure of the Vessels of the 

 Second Series. 



The cells of the second series of tubes' are considerably 

 smaller than those of the first series, and the nuclei, which are 

 round or oval, are much smaller. The nuclei are densely 

 chromatic; the chromatin granules are of the same color and 

 size as those in the nuclei of the first series. The cytoplasm 

 stains less intensely with eosin and is pinkish rather than 

 purple-pink. The lumen is very slight. There is a distinct 

 basement membrane and a nucleated peritoneum. 



The Vessels in the Wall of the Colon. 



Both cells and nuclei of the vessels in the wall of the colon 

 are very much smaller even than those of the second series. 

 The nuclei, which are proportionately large, are round or oval, 

 and densely chromatic, w4th small dark-stained chromatin 

 granules. The cytoplasm is homogeneous, and is not divided 

 itito areas; it stains less intensely with eosin than that of the 

 free portion of the tubes. The writer has not been able to find 

 any trace of a striated border lining the lumen. There is a very 

 delicate but distinct basement membrane, and a nucleated 

 peritoneum. 



4. THE SALIVARY GLANDS OF THE LARVA. 



The salivary glands of insects are not appendages of the ali- 

 mentary canal, but are independent ectodermal invaginations, 

 which open secondarily, if at all, into the mouth cavity. In 

 the larva of the alder flea-beetle there is a single pair of these 

 glands, more properly in this case to be called maxillary glands, 

 which open at the inner base of the maxilla. They are simple 

 tubular glands, short, lying entirely within the head, usually 

 extending along the ventral side nearly to the thoracic border, 

 and then bending up at a sharp angle, running nearly to the 

 dbrfeal body wall. 



Sections through the invagination of these tubes (see figure 

 33) show that the chitin of the central duct (which is differ- 

 entiated into a primary and a secondary layer) is continuous with 

 the cuticula of the body wall. There is no transition between 

 the hypodermis and the gland cells, but the glandular epithelium 



