NERVOUS SYSTEM OF CRUSTACEA 433 



made up of two lateral masses than in the other genera studied. 

 Four commissures may be clearly seen connect' ng the two lateral 

 parts. Four were also seen in Artemia and Branchipus but not 

 so clearly. The ventral ganglia of Estheria begin with the 

 mandibular and extend to the end of the body with a pair of 

 ganglia to each segment and with two commissures connecting 

 each pair (fig. 3). 



Cells of a number of types were found. In Branchipus they 

 are from 0.01 mm. to 0.05 mm, in diameter. The much smaller 

 but similar Artemia has smaller cells, the largest being about 

 0.02 mm. and the smallest about 0.005 mm. Two divisions of 

 cells may be made, the neuroglia cells and the nerve cells. The 

 neuroglia cells, small or large, were not so deeply stained in the 

 fibrillar area; they usually have granular nuclei. From whole 

 mounts and sections it was evident that the neuroglia nets are 

 much as described in other invertebrates. It is possible that 

 some of the small cells which seem to be nerve cells are neuroglia 

 cells. 



CELLS 



Practically all the nerve cells, especially of Branchipus, have 

 well-marked cell bodies filled with dark staining material and 

 clear nuclei containing nucleoli. A few nerve cells have much 

 clearer cytoplasm than the others. In the large cells especially, 

 tigroid substance may be seen even in surface views. In the 

 larger cells also the fibrillae are quite evident. The general shape 

 of the cells is spherical, but some are elongate. Most cells are 

 unipolar or bipolar, but a few are multipolar (figs. 5 to 13). 



Large, medium sized and small cells are found in the cellular 

 areas with no apparent special order, but the largest cells are 

 found at certain places at the margins of the ganglia. At least 

 one, sometimes two or three of the largest cells are located on 

 each side near the more caudal commissures of each ventral 

 ganglion. These in many cases send or receive processes to or 

 from the connectives. Perhaps they are cells in most cases with 

 long commissural fibers. 



