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PACIFIC SCIENCE, Vol. XIV, July I960 
trols. These represent the spots resulting from 
the presence of N-acetylglucosamine, the build- 
ing block of chitin. 
DISCUSSION AND CONCLUSION 
The presence of chitin as the principal con- 
stituent of the stomach teeth may not be sur- 
prising, considering that the hard structures of 
the anterior digestive tract of all gastropods 
tested have been shown to consist of chitin. 
However, the organic portion of the gastropod 
shell has consistently been reported negative for 
chitin in other snail groups tested and has been 
found so in this investigation in the amphibious 
prosobranch Oncomelania . The nature of the 
shell and the relative proportions of calcium 
and organic matter are very different in the 
gastropods possessing calcareous shells as against 
the largely organic, vestigial shell of most opis- 
thobranchs. At most the amount of organic 
matter in the calcareous type of shell of the 
former constitutes a periostracum or matrix. 
However, in many of the latter the vestigial 
shell is almost, if not entirely, composed of 
organic material. In the shell-bearing opistho- 
branch, Bulla, the organic matter is consider- 
ably less than in Aplysia and can be compared to 
that of the pulmonates, such as Helix and Vi- 
vaparus. The amount of calcium present in the 
aplysiid shell varies, some possessing little, if 
any, apparent calcareous layer, while in others 
a calcareous film or crust is formed on the 
inner surface of the organic shell. In A. calif ar- 
nica rarely more than a translucent film is pres- 
ent. The presence of an occasional thicker cal- 
careous layer in this latter species seems to be 
associated with a diet high in Corallina sp., a 
calcareous alga. Some species are said to nor- 
mally deposit a calcareous layer or crust. 
The enzymochromatographic method of chi- 
tin detection here adapted from existing 
techniques offers one very distinct advantage. 
As suggested by Richards ( 1951 ) , there may be 
chitins in a broader sense which are not per- 
sistent in the hot KOH treatment used in the 
chitosan color test and therefore are not de- 
tected even though they are made up of the 
requisite N-acetylglucosamine. These would be 
detected by the enzymochromatographic method 
described unless they are not attacked by the 
snail enzyme — which is unlikely. 
The presence of chitinase in the digestive 
gland of the large European snail, Helix po- 
matia, has been exploited in the past for the 
enzymatic dissolution of chitin (Karrer, 1930). 
Jeuniaux (1954) found a chitinase present in 
the digestive organs of H. aspersa , the common 
garden snail. 
SUMMARY 
The stomach teeth of Aplysia calif ornica and 
Bulla gouldiana were tested for chitin by the 
specific chitosan color test method and were 
found to be strongly positive. The organic shell 
of Aplysia calif ornica gave a positive chitosan 
and confirmatory test. The organic periostracum 
of Bulla gouldiana left some KOH-resistant 
material, giving positive chitosan color and con- 
firmatory tests. The organic portion of the shell 
of the amphibious prosobranch, Oncomelania, 
was not KOH-resistant and was negative for 
chitin. The stomach teeth of Aplysia were tested 
by enzyme digestion, followed by chromato- 
graphic analysis of the soluble residues, and 
showed the presence of N-acetylglucosamine 
comparable to that found in the commercial 
chitin used as controls. 
REFERENCES 
Jeuniaux, C. 1954. Sur la chitinase et la flore 
wacterienne intestinale des mollusques gas- 
teropodes. Mem. Acad. R. Belg. 28: 1-47. 
Karrer, P., and C. V. Francois. 1929. Poly- 
saccharide. Uber den enzymatischen Abbau 
von Chitin. Helv. Chim. Acta 12: 986. 
Kunike, G. 1925. Nachweis und Verbreitung 
organischer Skeletsubstanzen bei Tieren. Z. 
Vergl. Physiol. 2: 233. 
Pantin, C. F. A., and T. H. Rogers. 1925. An 
amphoteric substance in the radula of the 
whelk. Nature 115: 639. 
Richards, A. Glenn. 1951. The integument 
of arthropods. Univ. Minnesota Press, Min- 
neapolis. 
Roche, Jean, Gilbert Ramson, and Mar- 
celle Eysseric-Lafon. 1951. Composition 
