344 JouRNAL oF COMPARATIVE NEUROLOGY. 
This is especially so along the median line, where in some 
places they form chains uniting the dorsal and ventral nidi. 
Although this paper recognizes the same number of nidi 
in the brain as does KRIEGER (’88), yet the names given by 
him are not retained here, because some are misleading and 
others are cumbersome to handle. For instance what he calls 
the anterior nidus is on the dorsal surface of the brain and what 
he calls the posterior nidus is on the ventral side of the brain. 
“Outer nidus of the lateral swellings” is certainly cumbersome 
to handle. 
Below is tabulated the names used by KriEGER and the 
terms proposed and used in this paper : 
CELL NIDI OF THE DECAPOD BRAIN. 
KRIEGER’S names This paper’s names 
Anterior cell nidus (unpaired) |Dorsal nidus (unpaired) 
Inner nidus of the lateral swell-|Inner mushroom nidus (paired) 
ings (paired) 
Outer nidus of the lateral swell-|Outer mushroom nidus (paired) 
ings (paired) 
Outer nidus of the posterior|Latero-ventral nidus (paired) 
swellings (paired) 
Posterior nidus (unpaired) Ventral nidus (paired) 
Dorsal Nidus (figs. 1-3, 7-9, 17, 18, D.W.). This is a 
large cluster of cells which extends over most of the dorsal ~ 
(figs. I-3, 5, 7-9) and a large portion of the cephalic (figs. 15, 
17, 18) regions of the brain. The principal cells of this nidus 
are large and contain large nuclei and small nucleoli. Among 
these cells numerous neuroglia cells are distributed (fig. 32). 
On the dorsal surface of the brain of Nereis there isa 
cluster of pear-shaped cells which may be the homologue of 
this nidus. 
Outer and Inner Mushroom Nidi (fig. 1, O.M.N., 1. M.N.). 
These cell clusters resemble each other and differ from all others 
in having their cells arranged in rows which radiate from a com- 
mon curve (fig. 23). They will be described in full in connec- 
tion with the mushroom bodies. 
