— U — 



ganglion -cord/ it now lies in at least four segments, 

 namely, the third, fourth, fifth and sixth, its opening 

 lying at the base of the third extremity. 



There are two different parts of the gland which can 

 be distinguished, namely, the mouth end and the gland 

 proper. The mouth end is composed of cells in every 

 way resembling those that form the epidermis. Its nuclei 

 are oblong, and stain deeply with hsematoxylin. In this 

 part I observed no trace of cell-walls. The second part 

 builds up the chief bulk of the gland itself. It consists 

 of an unbranched tube, much convolved at its inner 

 end. The tube runs nearly straight from the surface up 

 to near the brain; next it bends backwards and runs in 

 almost a straight line till it reaches the sixth segment; 

 then it begins to twist and turn so much that it is 

 impossible to follow it further. As I have nowhere been 

 able to observe a branching of the tubes, I suppose that 

 it must be simple in its whole length, as in other 

 Arachnids. 



The cavity of the gland is about *01 mm. wide. The 

 cells composing the tube have very distinct cell-walls, the 

 cellplasm being very clear and staining very slightly. The 

 nuclei are perfectly round, and do not stain very deeply; 

 their diameter is '007 mm. They lie almost always on the 

 side of the cells nearest to the lumen of the gland, leaving, 

 however, a space between themselves and the cell-walls. 

 In this space the plasm seems at its thickest. The length 

 of the cells, measured from outside the gland to the cavity 

 of the gland, is *02 mm. 



The tube forming the gland itself is enclosed in a 

 sheath of flat cells, of mesodermatic origin, as in other 

 Arachnids. The space between the windings of the tube 

 is filled out by connective tissue. The whole gland is 

 likewise covered by an outer skin, the elements of which 

 somewhat resemble those forming the sheath of the tubule. 



5. The Central Nervous System. — The nervous 

 system now consists of the cerebral ganglion, the ventral 

 ganglion -cord, and the nerves. 



When compared with the fourth stage, the ventral 



