No. 3.] NERVOUS SYSTEM OF CYNTHIA PARTITA. 103 



These chromatin granules are held in place, as is the nucleolus, 

 by a finely fibrous achromatic network. In large cells one 

 nucleolus is always present, rarely two. If two are present, 

 one is larger than the other. The nucleolus is frequently 

 observed to be vacuolated. It is often found suspended in the 

 achromatic network of the nucleus, but just as frequently 

 is it found against the nuclear wall. In deeply invaginated 

 nuclei the nucleolus is 



found against the nu- 

 clear wall at the bottom 

 of the invagination, as 

 if the wall had been 

 pushed in until it had 

 reached the nucleus. 



In the smaller cells 

 of old specimens as 

 well as the cells of 

 young animals quite a 

 different state exists. 

 The chromatin gran- 

 ules are more evident, 

 being larger, staining 

 deeply, and apparently 



n n. 



p.c. 



Fig. 2. — Cross-section of periphery of brain of young 

 Cynthia, showing absence of connective-tissue sheath. 

 p.c, large peripheral ganglion cells; n.n., neuroglia 

 nuclei; «., neuroglia and nerve fibers. Von Rath. Iron- 

 haematoxylin. ^V x oc. 6 (Zeiss). 



more numerous than 

 in the large cells. The 

 nucleus, as has been 

 noted, is much larger 



comparatively than in larger cells. The nucleolus is small. 

 There appears at first sight little difference between these 

 nuclei and those of the so-called neuroglia cells, but a closer 

 investigation shows the latter to be more oval and elongated 

 and to have a less prominent nucleolus than the nerve cell (see 

 Fig. 2). In ganglion cells of young specimens killed a few 

 days after metamorphosis the nucleus is very rich in chromatin, 

 and presents much the same aspect as is shown by the smaller 

 ganglion cells of the adult specimens. The nucleus is pro- 

 portionately very large, occupying the greater part of the cell- 

 body. In the larger peripherally placed cells of the young 



