THE CARNIVOEOUS SLUGS OF SOUTH AFRICA. 133 



glandular tissue becomes still scai^cer towards the hind end, 

 and disappears entirely just before the vesicle is reached, 

 while in the other races of A. gibbonsi and in A. parva 

 the last few millimetres of the duct are quite destitute of 

 gland-cells. Finally, in A. dimidia the glandular tissue only 

 extends along half the length of the duct, the posterior half 

 being entirely without it, and therefore much narrower than 

 the anterior half (PI. XIII, figs. 54, 59, and 60). 



PI. XTV, fig. 63 shows the structure of the glandular tissue 

 near the front end of the pedal gland in A. gibbonsi 

 rubella. It will be seen that among the large oval gland- 

 cells, which taper towards the duct, there are scattered con- 

 nective-tissue cells with conspicuous rounded nuclei, and 

 there can be little doubt that it is from these cells that the 

 glands are formed. Similar cells occur near the front end of 

 the pedal gland in A. dimidia, but further l)ack, near the 

 hind end of the anterior half of the gland, no such cells 

 occur, and a transverse section has the appearance shown in 

 PI. XIII, fig. 59. Possibly the absence of connective-tissue 

 cells from this region may be correlated with the absence of 

 gland-cells still further back. The posterior part of the 

 gland will probably be the first to be formed in development, 

 and if all its cells, apart from those which form the duct 

 itself, are converted into glands, there will be nothing left to 

 replace these when they die and are discharged into the duct ; 

 for according to Andre ^ the gland-cells perish after a certain 

 time and need to be replaced. 



Mr. Collinge- has stated that the pedal gland of Apera 

 sexangula contains "a large series of microscopic chitinous 

 (?) dart-like bodies," but his figures leave little doubt that 

 these are merely the solidified contents of the glands. In 

 specimens preserved in alcohol this congealed secretion 

 appears through a simple lens as numerous white specks, 

 which often give a glistening appearance to the pedal gland. 



' 'Revue Suisse de Zoologie,' 1894, vol. ii, pj). 310, 311. 

 2 ' Ann. Mag. Nat. Hist.' (6th ser.). 1897, vol. xx. p. 223. pi. v, figs. 

 4, 5. 



