484 PATTEN AND HAZEN. [Vol. XVI. 



the fourth lobe. From the end sac many tubes lead forward 

 into the stolon. The latter consists of a coarse network of 

 anastomosing tubes, from which branches are given off that 

 extend along the median dorsal face of each lobe, diminishing 

 in size as they go. The entire substance of the lobes may 

 be colored a deep red by injecting red gelatine into the main 

 duct. 



Along the walls of the duct are here and there short, blunt 

 evaginations or pockets ending blindly. In some cases the 

 pockets of one tube may unite with those of another, thus form- 

 ing communications between the separate coils (PI. XXVII, 

 Figs. 81 and 82, po. and c.n.t.). They are most numerous in 

 the extensive coil lateral to the fourth nephric lobe. 



IX. Cells of Doubtful Significance. 



During the Trilobite stage certain cells appear on the 

 nephridial lobes, which may be readily recognized by pecul- 

 iarities of shape and coloring (PI. XXV, Fig. 45 ; PL XXVIII, 

 Figs. 74 and 80, s.r.c). They are dark purple when stained in 

 Lyon's blue and borax carmine. These cells were found only 

 in the vicinity of the hollow nephridial tubules, with which they 

 were often so closely connected that it was impossible to ascer- 

 tain with certainty whether they were inside or outside the 

 tubules. Occasionally they were on the outer margin of the 

 tubules, and it would then appear as if they were about to 

 separate from them (PI. XXVIII, Fig. 74, c). In PI. XXVIII, 

 Fig. 80, at the dorsal side of the end sac, about a dozen were 

 collected, which suggested a point of proliferation either by cell 

 division among themselves or from the nephridial tubules or 

 sac. At the left {v.c.) one of the cells is much larger than the 

 others and shows vacuolations in the protoplasm. A few of 

 these cells were found in the second larval stage, as shown in 

 PI. XXV, Fig. 46, r.c.y and also in the region of the heart (PI. 

 XXVIII, Fig. y6, r.c), after which they entirely disappeared. A 

 large number of granular cells appear at this time, and it seems 

 probable that they are different conditions of the same cells, 

 although no convincing proof of it could be found. 



