214 
lethal effects masked by the respiratory arrest. 
However, respiratory arrest seems to be the 
limiting factor in birds and mammals, though 
a suggestion of other contributing effects is 
noted in the chick. Studies on isolated prepara- 
tions are now in progress and will be reported 
later. 
At the present stage of the study it is im- 
possible to postulate the function, if any, or the 
ultimate source of the toxin. The absence of 
any method for the animal to inject the toxin 
along with the high dosages required to be 
effective orally would seem to preclude any de- 
fensive use. However, both concentration of the 
toxin from the seaweed diet or an endocrine 
function may be considered as possibilities. 
SUMMARY 
1. The digestive gland of Aplysia calif ornica 
and A. vaccaria contain a water- and acetone- 
soluble toxin. 
2. Crude extracts produced muscular weak- 
ness and death by respiratory arrest when in- 
jected intraperitoneally into various laboratory 
animals or given orally at about 12 times the 
IP dose. 
PACIFIC SCIENCE, Vol. XV, April 1961 
3. Frogs survived a respiratory arrest and 
complete paralysis for 13 hr. When extracts are 
given in much larger doses, death ensues from 
causes not yet determined. 
4. From observation of these symptoms, it is 
suggested that the primary lethal effect in mam- 
mals and birds is respiratory arrest, though 
other less dominant lethal effects seem to op- 
erate in the frog. 
REFERENCES 
Dixon, W. J. 1959. {A later, as yet unpub- 
lished, simplification of his method as pub- 
lished by A. W. Kimball, W. T. Burnett, Jr., 
and David G. Doherty, 1957.} Chemical pro- 
tection against ionizing radiation. Rad. Res. 
7: 1-12. 
Johnston, George. 1850. Introduction to Con- 
chology; or Elements of the Natural History 
of Molluscous Animals. J. Van Voorst, Lon- 
don. 
Pliny, Secundus. ca. a.d. 60. Historia Natu- 
ralis, Lib. 9, 32. 
Winkler, Lindsay R. 1956. The biology of 
California sea hares of the genus Aplysia. 
Dissertation, Univ. So. Calif., Los Angeles. 
