AN HEREDITARY TUMOR • 519 



loosely connected with one another. Granules of brown pig- 

 ment are normally present in these cells. The ganglion forms a 

 crutch over the anterior portion of the proventriculus, giving off 

 ganglionated nerves to it and the chyle stomach, also on each 

 side to the salivary glands, terminating in ganglionated plexuses 

 in the wall of the gland. A dorsoventral section of the ganglion, 

 (fig. 5) , shows an early stage in the development of the tumor. 

 There is an increased number of cells as compared with the num- 

 ber of cells present in the ganglion of normal larvae. There is 

 also an increase in the amount of pigment. Figure 9 shows a 

 later stage in development, where the cells have become compact 

 with pigment. 



Very often, when the proventriculus ganglion becomes affected, 

 the cells of the salivary glands become loaded with pigment, as 

 shown in figure 7. Sometimes only one gland becomes affected 

 (as shown in fig. 5, Jour. Cane. Res.), where the left gland is en- 

 tirely permeated by pigment and the entire gland seems hard 

 and, in places, very much shriveled. In the Jour. Cane. Res., 

 July, 1918, figure 2 shows the ends of the two glands affected. 

 " In the anterior end of the salivary glands are the imaginal 

 cells of the adult salivary glands. These cells have also been 

 found affected as have the imaginal cells of the proventriculus 

 and also those of the chyle stomach. The oesophageal ganglion 

 has in two cases been found increased in size and abnormally 

 loaded with pigment, and in these cases the infection has spread 

 to the imaginal cells of the oesophagus. 



The tumor found so often in the posterior end of the larva 

 takes its origin in a group of embryonic cells closely associated 

 with the nerve cells of the pericardial plexus, found on the 

 margin of the pericardial septum. The nerve cells are large, 

 bipolar cells with large vesicular nuclei and distinct nuclei. 

 They are loaded with brown granular pigment in the normal 

 larvae. Figure 8 shows the initial stage in the production of 

 pigment in a group of cells underneath the pericardial septum. 

 Figure 6 shows a great increase in the number of cells and a 

 tendency to push the pigment cells toward the peripher}^ Fig- 

 ure 1 from the report in the Jour. Cane. Res., July, 1918, is a 

 section of a matured tumor developed in this region. 



