Lipids of the Nervous System of the Squid Loligo Pealii

1. The concentration of total phospholipin, free and total cholesterol, cerebroside (glycosphingoside), monoaminophospholipin (phosphoglyceride) and lecithin (phosphatidyl choline) was determined in the central ganglia, pallial nerve, whole giant fibre of the stellar nerve, and axoplasm of the giant fibre of the squid, Loligo pealii. From these figures was calculated the concentration of ester cholesterol, sphingomyelin (phosphosphingoside) and kephalin.

2. The concentration of total phospholipin in the central ganglia was of the same order as that found in mammalian brain, but the concentration of cholesterol and sphingomyelin was less.

3. The concentration of lipids in the pallial nerve was less than that in the central ganglia. The concentration of lecithin exceeded that of kephalin, while sphingomyelin accounted for higher percentage for phospholipin than in the central ganglia.

4. The concentration of lipids in the whole giant fibre of the stellar nerve, less than that in either the central ganglia or in the pallial nerve, was greater than that in the axoplasm.

5. The results are consistent with the view that the axon of the giant fibre of the stellar nerve is surrounded by a thin lipid-containing sheath.

6. Neither cerebroside nor ester cholesterol was found in the nervous system of the squid.

7. With the exception of cerebroside, the relative concentration of lipids in the central ganglia and in the axoplasm of the giant fibre resembled that in parts of the nervous system of man that contain relatively few myelinated fibres, i.e. the grey matter of the brain of the adult or either the grey matter or the white matter of the brain of the newborn infant.

A Bifunctional Single Motor Axon System of a Crustacean Muscle

It is shown that the opener muscle of the hermit crab, Eupagurus bernhardus L., receives a single motor axon. Stimulation of this axon results, when appropriate stimuli are used, in two types of contractions comparable with the fast and slow contractions of doubly motor-innervated crustacean muscles. The theoretical implications of this finding are discussed and a hypothesis offered to explain the mechanism which makes the two contraction types possible. The physiological and anatomical features of the innervation of the four most distal muscles in the legs of Eupagurus are described.

The Pigmentation of Cavernicolous Animals

1. The visible coloration of three species of amphipod Crustacea (Gammarus pulex, G. marinus and Orchestia gammarella) was found to be due almost exclusively to carotenoid pigments, including in each case a proportion of an astacin-like carotenoid acid.

2. No carotenoid pigments could be demonstrated, even in traces, in three species of the cavernicolous Amphipod genus Niphargus.

3. Carotenoid pigmentation is thought to be characteristic of Amphipoda and would therefore be the ancestral pigment of the cave forms. The lack of pigment in cave Amphipoda may be due to absence of light; it is not due to lack of carotenoid pigments in the food.