404 THOS. H. MONTGOMERY ir, 
66, 68, 70, 73—75, Pl. 41) in the medio-ventral line of the body, 
below the intestine (Int) and separated from it by a layer of small- 
celled parenchym (a deflection of the walls of the mesenteries), ele- 
vated a short distance above the musculature (Musc) of the body 
wall and attached to the hypodermis by a median band, which will 
be called the neural lamella (N.L). 
One adult female fixed in 4°, formaline was cut into short pieces 
and all of these imbedded in paraffine; a series of sections of 6?/, u 
thickness covering at least two slides, was cut of the greater number of 
each of these pieces, so that the relations of the nervous system might 
be studied in the various regions of the body without the necessity of 
the great labor of sectioning an entire individual. This fixation is 
most excellent for the nervous elements. Series of sections of other 
individuals, fixed in various other fluids were also studied as a control. 
The iron-haematoxylin method of staining proved most satisfactory 
for the determination of the details; for the study of the chromo- 
phobic nerve cells a rather darker stain is necessary, for the chromo- 
philic cells a fainter stain; in general the destaining should proceed 
until the cytoplasm of the hypodermis has given up its stain almost 
entirely. 
Two main elements may be distinguished in the nerve cord: 
chromophilic nerve cells and chromophilic nerve fibres, 
and chromophobic nerve cells and chromophobic nerve 
fibres, the former being those which unite most strongly with the 
iron-haematoxylin stain, the latter those which unite with it less 
strongly. 
The chromophobic elements. The chromophobic nerve 
cells (CRD. CC: Bigs. 22,024, 25 Pl. 38: Figs; 26151032 ra 
on the ventral and lateral aspects of the nerve cord, and in only one 
or two sections out of the hundreds carefully studied were any found 
upon the dorsal side. On the lateral aspects they form for the most 
part a single layer, while ventrally they may be from two to four or 
five deep. They are characterized by a regularly spherical or oval 
nucleus (N Figs. 29, 30, Pl. 39), with one true nucleolus and very 
little chromatin arranged in a delicate reticulum so that they stain 
faintly. Their cytoplasm appears very finely granular, is nearly homo- 
geneous only occassionally somewhat vacuolar, and appears to contain 
neither centrosomes nor attraction spheres. These cells on the lateral 
aspects of the cord are comparatively uniform in size and small. But 
on the ventral aspect are found two varieties of these cells: small 
