AND EMBRYOLOGY OF LIMULUS. 45 



Fig. 6. Section of left side of brain of -Limulus, below the ocellar nerve, passing through the lower set of 

 tegumental nerves. The fibrous area [/"a] much branched, and still much greater than on the right side 

 [/a']. A number of large ganglion cells are present at the posterior outer portion of the brain. Magnified 

 30 diameters. 



Fig. 7. Section through left side of brain of Limulus, below any of the nerves, quite near the base of 

 the brain, and showing how much the nucleogenous bodies have encroached on the fibrous area [^a]. 



Figs. 1 and 2, were cut from the same brain ; figs. 3, 4, 5, 6 and 7 from another brain ; and were selected 

 from about ninety other sections. 



Note. — All the figures in plates 1-7 were drawn by the author, except plate 2, fig. 1, drawn by P. Roetter ; 

 and plate 1, fig. 1, and all the figures on plate 2 (except fig. 1;, which were drawn by J. S.Kingsley. ' 



Zoological Laboratory of Brown University, 

 Providence, R. I., May, 1880. 



ERRATA. 



Page 10, line 30, for Arthopoda reai^ Arthropoda. 



Page 16, line 1 from bottom of footnote, for Tottennia read Tottenia. 



Page 23, line 25, for (Fig. 9, rt) read (Fig. 9, rt ?). 



Page 26, line 6 from bottom for " or lens-epithelium " read " lens-epithelium.' 



Page 29, line 14, for analagous read analogous. 



Page 29, line 37, after the word but dek that. 



