494 



PATTEN AND HAZEN. 



derm. The largest of these cells lie beyond the lateral base of the appendage. 



X 200. 



Fig. 40. A longitudinal section from an embryo of about the same age as 

 that in PI. XXIII, Figs. 30-32. The somites of the thorax have disappeared, 

 except the one in the fifth appendage, which remains as the end sac to the nephrid- 

 ial duct. Bunches of nephridial cells are found in the chelicerae and in the second, 

 third, and fourth appendages. Nephridial cells appear later in the sixth append- 

 age. X 100. 



Fig. 41. Longitudinal section through the fourth and fifth appendages. The 

 nephridial cells are filled with large granules, among which the larger nuclei are 

 visible. Often the cell boundaries were very indistinct or else entirely invisible, 

 giving the appearance of several nuclei in the same cell. In the fifth appendage 

 the end sac shows as a closed cavity, with a few of the larger nephridial cells on 

 its ventral wall. X 400. 



Fig. 42. Longitudinal section through the fourth and fifth legs. It shows a 

 bunch of large, granular, nephridial cells at the base of the fourth leg. In the 

 fifth leg the end sac is lined with granular cells which are similar to those in the 

 fourth leg, except that they are smaller. There is a blood space between 

 the appendages and at the apex of the appendages, x 300. 



