70 JOUENAL OF ENTOMOLOGY AND ZOOLOGY 



In addition to these there were ten or more specimens collected 

 that were not determined, some were immature, others were injured. 

 In all about 250 specimens were collected. 



The largest number were of three or four kinds. In spite of 

 some wandering the pycnogonids seemed to resemble their surround- 

 ings to a remarkable degree, either in color or lack of color in the 

 body and in the form and shape of the body and legs. 



(Contribution from the Zoological Laboratory of Pomona College) 



The Central Nervous System of Nebalia 



WILLIAM A. HILTON 



A number of specimens of Nebalia bipes Fab. were fixed in vari- 

 ous ways, serial sections were made and stained in Delafield's hema- 

 toxylin, carmine and iron hematoxylin. The last stain gave the 

 best results. 



The brain is composed of three parts of unequal size. The 

 optic lobes connected with the stalked compound eyes are the largest 

 of the three divisions. Due to the compound eyes this part of 

 the brain is complex. A median longitudinal section through an 

 optic lobe shows an arrangement of cells and fibers as follows: 

 Next the eyes there is a rather thick, dense layer of cells chiefly 

 noticeable because of their nuclei ; back from this a smaller crescent- 

 shaped mass of fibers is evident, followed by a zone of crossed 

 fibers and scattered cells. The cross fibers are connected with a 

 central rounded core of fibers which is separated slightly from two 

 other masses. All are largely surrounded by cells. 



Cross sections of the optic stalk or lobe give little indication of 

 the several divisions of cells and fibers, the general appearance for 

 most of the distance being of a central core of fibers surrounded 

 by densely packed cells. Towards the junction of the lobes with 

 the brain the cells less uniformly cover the central fibers. After 

 the two lobes approach each other, the masses of cells on either 

 side are massed together but not fused or united across the middle 

 line, although the two lateral parts are closely applied to each 

 other. Dorsally for a short distance, a thin band of cells which 

 may not be functional nerve cells arch over and connect the two 

 lateral halves of the brain, leaving a small cavity just below, which 



