TENTACULAR FUNCTION IN TRAIL FOLLOWING BY THE PULMONATE SLUG LIMAX PSEUDOFLAVUS EVANS

Comparison of the behaviour of slugs before and during trailfollowing shows that there is no change in their rates of locomotionbut that there are decreases in measures of tentacle activity(distance moved and the frequency of substrate contacts) duringtrail following. Bilateral amputation of tentacles has the generaleffect of slowing the speed of locomotion whether trail followingor not, and preventing the decrease in tentacle activity duringtrail following. Amputation of the anterior tentacles results in a decrease inthe accuracy with which trails are followed. Amputation of theposterior tentacles on the other hand, results in a decreasein the frequency with which slugs turned onto trails. Removalof all the tentacles prevents trail following. It is concludedthat the posterior tentacles are concerned with the detectionand identification of trails which are subsequently followedand that the anterior tentacles normally control the behaviourof the slug on the trail. (Received 22 May 1984;     

Elimination of species before cluster analysis

Previous attempts at selecting species to eliminate are criticized and a method depending upon interspecific dissimilarities is outlined. It was tested using a matrix of 24 samples by 71 species, and shown to be viable and much more economical to operate than an alternative method which was developed and discarded. It still involves the arbitrary choice of a cut-off level, and a parallel consideration of abundance values is advised. The method was assayed by performing cluster analysis with and without exclusion of species.     

Zaire butterflies and faunal diversity in the tropics

Samples of butterflies were collected along the Zaire River from its source to Kisangani and in the Ituri region. The number of species flying in the same area has been estimated wherever possible, and the degree of faunal similarity at different sites. The number of species increases as one proceeds north from 50–100 to 100–150, and the fauna is separable into two groups. The difference in faunal composition and diversity is related to the southern boundary of the rain forest. The comparative poorness of the butterfly fauna in tropical Africa compared to tropical South America is discussed, with reference to the parallel difference in the bird faunas of the two continents.     

Argon,xenon, hydrogen,and the oxygen consumption and glycolysis of mouse tissue slices

The effects of xenon, argon, and hydrogen on the aerobic and anaerobic metabolism of mouse liver, brain, and sarcoma slices have been investigated. Xenon was found to alter the rates of metabolism of these tissues in a manner almost identical with helium. The gas increased the rate of oxygen consumption in all three tissues and significantly depressed that of anaerobic glycolysis in brain and liver. The depression of glycolysis in sarcoma was less pronounced and not highly significant. Although both the magnitude and statistical significance of the effects observed with argon were much smaller, there was a seeming adherence to the general pattern established by xenon and helium. Hydrogen while remaining essentially ineffective insofar as oxygen uptake was concerned, depressed glycolysis in both liver and brain slices but did not significantly affect sarcoma slices. The following points are stressed in the Discussion: (1) the magnitude and direction of effects exerted by helium, argon, xenon, hydrogen, and nitrogen do not conform with the relative values of molecular weight, density, and solubility of these gases; (2) the effect of these gases on tissue metabolism does not necessarily parallel that exerted upon the whole organism.