ANATOMY AND CLASSIFICATION OP THE ARENICOLIDJ:. 569 



alveolar zone and if,s neuroglial envelope are seen. A few neuro-fibrillse are 

 shown at Nllee. enclosed in a dense glia-slieatb. 

 Corrosive-acetic, Apathy's ha^matein 1 A. X 500. 



PLATE 29. 



Fig. 78. — A portion of the nerve-cord of a young specimen of A. Grubii, 

 78 mm. long, to show the giant-cells and spinal nerves in relation to the 

 annuli. The cut ends of the neuropodial chatse of the fourteenth and 

 fifteenth chsetigerous segments are shown. Reconstructed from horizontal 

 sections. X 25. 



Fig. 79. — Plan of the entire nerve-cord of a young specimen of A. Grubii 

 78 mm. long, to show the position of the giant-cells. The transverse lines 

 mark the level of the neuropodia, the numbers of which are given at the sides. 

 The length of the cord in the drawing is twenty times its actual length.. The 

 breadth of the cord and the size of the nerve-cells are fifty times the actual. 

 Reconstructed from about 5000 sections. 



Fig. 80. — A portion of the nerve-cord of a specimen of A. marina 17-5 

 mm. long, to show the giant-cells. The section extends from the eighth to 

 the nineteenth chsetigerous annuli. Reconstructed from sagittal sections. 

 X 20. 



Fig. 81. — A portion of the nerve-cord of a specimen of A. cristata to show 

 two of the segmentally enlarged giant-cells, x 2. 



