THE ENUMERATION OF FAECAL STREPTOCOCCI IN FOODS, USING PACKER'S CRYSTAL VIOLET SODIUM AZIDE BLOOD AGAR

SUMMARY: Packer's crystal violet sodium azide blood agar (Packer, 1943) used in poured plates at 36·1°, gave satisfactory recovery of pure cultures of Lancefield group D streptococci and completely inhibited the growth of 11 other species of aerobic and anaerobic food bacteria, including Strep. lactis (5 strains). Later, however, one group N streptococcus was obtained which did grow in Packer's agar at 36·1°. To eliminate this organism the incubation temperature had to be increased to 39·5°, using agar strips (Stirling et al. 1950) incubated in a water bath to secure strict temperature control. Under these conditions the recovery of typical group D streptococci was never consistently below 50% of the count in tryptone dextrose yeast extract agar at 31·1°.     

INTEGRATION AND SYMMETRY IN BEROE

Despite the fact that certain prominent structures such as theeight comb-rows at first suggest an octomerous radial symmetryin ctenophores, close examination of their anatomy reveals ratherthe existence of two main planes, the sagittal and the transverse.Further, in certain forms in which one plane or the other hasbecome predominant, an apparent bilateral symmetry emerges. Relationships between anatomical and physiological symmetrywere looked for by studying the behavior of Beroe ovata andBeroe forskalii, both with regard to coordinated ciliary movementsbetween the comb-rows, and to the postures assumed during locomotion,balance, and rest in intact animals, and in animals from whichthe aboral organ had been removed. Swimming behavior is found to exhibit an octomerous functionalsymmetry. Bendings and vertical balance, however, show a tetramerousorganization. In the last case the unique properties of thestatocyst, with a structure characteristic of a regulator ofcybernetic patterns, the machines of which are the comb-rows,permit the most efficient integration of all the phenomena involvedin maintaining the vertical position. Finally the resting horizontalposition reflects a physiological bilateral symmetry basic tothe sagittal plane.     

Phylogeography of two parthenogenetic sawfly species (Hymenoptera: Tenthredinidae): relationship of population genetic differentiation to host plant distribution

This study compares the population genetic structure of two obligate parthenogenetic sawfly species, Aneugmenus padi (L.) Zhelochovtsev and Eurhadinoceraea ventralis (Panzer) Enslin (Hymenoptera: Tenthredinidae). Allozymes were used to detect genetic differences in larvae collected at different sites in six European countries. For A. padi , scoring six polymorphic enzymes revealed the existence of five dominant, widely distributed clones and several more with only very few individuals occurring locally. The clonal diversity and identity differed across collection sites, with up to at maximum eight clones coexisting at a single locality. In contrast, in E. ventralis , individuals from different localities were all monomorphic for at least six different enzymes and are therefore assumed to belong to the same clone. Differences in population genetic structure of these sawfly species can be related to the differing distributions of their host plants: the fern, Pteridium aquilinum , the host of A. padi , has been an invasive species for more than two hundred years. Spread of clones of A. padi is likely to have closely followed the complex invasive pattern of spread of the plant. Larvae of E. ventralis were collected from local, horticultural plantings of Clematis spp. of recent origin probably with gardeners having traded plants infested with the sawfly.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 219–227.