184 



N. CHALAZONITIS 





Fig. 19. Electron micrography of Aplysias soma. 



Among the osmiophilic particles such as mitochrondria, endoplasmic reticulum, 

 the grains (g) — or 'iipochondria*', or "lipoid globules" — of from 01 to 0-8 /i 

 diameter are the most numerous and by far the most osmiophilic. Preliminary 

 observations on the ultrastructure of these grains have been described elsewhere 

 (Chalazonitis and Lenoir, 1959). The larger ones are aggregated at the peri- 

 phery of the soma forming groups of variable density, the highest being observable 

 in the axon hillock area. Very often in the other somatic areas the greater density 

 of the lipochondria coincides with the greater thickness of the somatoplasm. The 

 perinuclear cytoplasm is essentially formed of fine osmiophilic granules which 

 correspond to the Nissl substance in this neuron. The same cytoplasm region 

 shows digitations and folds sometimes penetrating deeply into the nucleus and 

 forming bridges there. The thickness of the cytoplasm is not uniform all around 

 the profile of the nuclear membrane, the greater thickness observed just opposite 

 to the most numerous digitations of the perinuclear region. Scale: 5 /(. 



Table 2. The pigments present in Aplysia fasciata or depilans 



NERVE CELLS 



It must be emphasized that the hpochondrial haemoprotein stores the 

 oxygen of the soma. A rough estimation gives a figure of 3 10"'^ M of 

 haemoprotein/g wet neuron, or roughly ten times more per gramme of wet 

 Upochondria. 



