walling: the acridid^an heart. 367 



per cent, formalin and iron-hsematoxylin, show them as illus- 

 trated in figure 4. These cells more nearly resemble the gan- 

 glion-cells of the vertebrates than any other structures thus far 

 found. They have a distinct, dark-staining nucleolus. The 

 nucleus is quite clear. The cytoplasm is very dense through- 

 out the whole cell. 



It is very easy to call these ganglion-cells when one is espe- 

 cially looking for that kind of cells, and yet there is much evi- 

 dence against their being of this character. 



First, in only a few cases have I seen any processes resem- 

 bling nerve-fibers leading from these cells. Second, they are 

 not confined to any definite place, as one would expect to find 

 ganglion-cells. I have noticed, however, that they are very 

 much more numerous at the place of attachment of the alary 

 muscles to the chitin, and if they are ganglion-cells they may 

 control the action of these muscles as well as those of the 

 heart. 



A ventral sinus of similar structure and with similar pulsa- 

 tions has been described as lodging the ventral nerve chain, 

 and these same cells are to be found in this sinus. Ransom 

 gives this as one reason why they are not ganglion-cells, but 

 it seems to me that it is an evidence for, rather than against, 

 such a view. Since these ventral pulsations are similar to the 

 dorsal, it would be expected that they were controlled by the 

 same kind of cells. 



Figure 9 is a cross-section through a thoracic ganglion. 

 The methods used did not bring out the nerve- or ganglion- 

 cells very satisfactorily. In fact, very few structures in the 

 least resembling nerve-cells could be seen anywhere excepting 

 around the edges and near the middle of the section. The 

 large round cells scattered around the edge of the section some- 

 what resemble the large cells seen at figure 6, except that the 

 nucleolus does not stand out so distinctly. In fact, the whole 

 cell does not show a definite structure. 



From the results thus far obtained I cannot therefore say 

 that nerve- or ganglion-cells do not exist within the heart- 

 structure of the grasshopper, and I believe they are present 

 and need only the proper stain to prove their existence. 



