Structure and Polarity of Electric Motor Nerve-Cell in Torpedoes. 251 
seen by Magini in several cases and ascribed by him to the physio- 
logical activity of the cell. Coggi contended that this space was due 
to the strong osmotic action between a fixing fluid and the fluids of the 
cell. 
The experiment performed by the writer was to place a brain of 
Torpedo ocellata (No. 21) in some light fluid, 95 per cent alcohol being 
used. This fixed the tissues, and when sections were cut it was found 
that the osmotic action had forced all the contents of each nucleus in 
a centripetal direction, leaving the spaces described by Magini on the 
outer side. These meniscoidal spaces are not outside of the nucleus, 
however, but are formed within its nuclear membrane, which retains its 
rounded shape. All contents of the nucleus take part in the movement, 
leaving an absolutely vacant space to form the meniscus. 
As text-figure 5 will show, this action is centripetal with reference 
to the mass of the brain, so that laterally placed cells have the meniscus 
on their outer lateral side and some placed on the under side of the edge 
of the lobe have it placed nearly on the ventral side. Magini overlooked 
these fewer exceptions to the general conditions when he stated that 
the meniscus was always placed dorsally, in addition to his mistake of 
assuming that the neurite always left the cell in a ventral direction 
and that the physiological action of the cell as described by him was 
dorso-ventral in direction. 
SUMMARY AND CONCLUSIONS. 
The net result of the three gravity experiments on torpedoes Nos. 3, 
4, and 20 seems to show that the plasmosome is the heaviest body in 
the nucleus, undoubtedly heavier in actual weight than the chromatin 
bodies and probably of a greater specific weight than any of the other 
nuclear organs, with the possible exception of the karyosomes. In 
young fish this plasmosome seems to have a central or general distri- 
bution, while in older or larger fish it acquires a constantly increasing 
ventral orientation, which the writer believes due to its increasing size 
and weight, together with a less resistant condition of the nuclear 
content to its slow movement through its mass. It may be said (and 
the observations, as shown in the table, bear it out) that in the small 
specimens of Torpedo under 12 cm. in length, nearly all cases show no 
orientation. From 12 cm. up a slowly increasing and quite irregular 
orientation in the ventral direction takes place, due to the increasing 
weight of the plasmosome, and greater or less in amount according to 
the resistance to its movement offered by the physical condition of 
the nuclear content. This content must be very slightly modified in 
its solidity, viscosity, etc., by food, by depth and water-pressure, and 
by individual variation. Such modification, however slight, would 
account for the variation in the amount of orientation found in different 
fully grown fish. 
