34 



size and tlie prnrainence of their nuclei they have been 

 regarded by previous writers as being the glands ^hich 

 provide the secretion which moistens that organ. 



7. The Cephalic Glands and Ventral Groove. 



In Anurida three pairs of cephalic glands are present, 

 two of which discharge their secretion into the ventral 

 groove, and the third pair open into the buccal cavity and 

 are to be regarded as salivary glands. Three pairs of 

 cephalic glands have also been made out by Willem and 

 Sabbe in Sminthttrus (28), by Willem in Orchesella (26), 

 and by Hoffmann in Tomocerus (12). 



The salivary glands of Anurida are lodged in the 

 hinder region of the head, one on either side (Plate VI., 

 figs. 63 and 65). They are composed of groups of acini, 

 and each acinus consists of a group of eight or nine very 

 large cells, which are disposed in a radial fashion around 

 a central ductule {dtl. in fig. 63). The cells of these 

 glands have very large nuclei, rich in chromatin, and a 

 considerable portion of the inner half of each cell is filled 

 with a dense and compact mass of secretory granules 

 [s. g.). The ductules are of very small calibre and are 

 intra-cellular at their commencement ; a little lower down 

 they converge and unite with those from neighbouring 

 cells to form a fine canal, which becomes inter-cellular in 

 structure. The canals from adjacent acini in their turn 

 unite with one another to form the main duct of the gland. 

 This duct (fig. 67) is composed of flattened cells, con- 

 taining small elongate nuclei ; both it and all other parts 

 of the glands are invested internally and externally by a 

 delicate membrane. The course of the duct is difficult to 

 make out among the numerous other structures of the 

 head, but it appears to converge with its fellow, from the 

 opposite side, towards the median line and to approach 



