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THEODORE H. BULLOCK 



missing in the light microscope. It must be concluded that the most hkely 

 anatomical basis is a connection of low electrical resistance somewhere 

 between the processes of the cells, in the neuropile. This would resemble the 

 connections believed to account for electrotonic communication between 

 neurons in the lobster cardiac ganglion (Watanabe and Bullock, 1960) and in 

 the supramedullary ganglion cell cluster of puffer fish (Bennett, 1960). 



Fig. 7. Giant axons intimately entangled in the neuropile; small fibered neuropile 

 to the right. Calibration; 100 micra. 



Very little is known about the axons of the giant cells. In our preparations 

 (Fig. 8) they measure up to 45 ■ 85 micra in diameter close to the ganglion 

 in the right pleurovisceral connective {A. californica off. 18 cm relaxed 

 length, with largest giant nerve cells of 350 micra diameter); 35 micra is a 

 more representative figure in the connective farther from the ganglion. Dr. 

 Batham has prepared excellent electron micrographs of transverse sections of 

 nerves. While the truly giant fibers were not encountered, she observed that 

 the larger axons (5-10 micra) in the sections always exhibited a complex, 

 infolded appearance (Fig. 6). Corresponding exactly to the findings of 



