Formation of Basal Bodies in Ciliary Epithelium of Molluscs Buccinum undatum L. and Lymnaea stagnalis L.

Electron microscopic studies of the leg ciliary epithelium was carried out in two mollusks. In the epithelium of the leg of adult animals, the centrioles were mostly formed de novo with participation of deuterosomes during the formation of basal bodies. Transformation of the centriolar cylinder in a mature basal body is accompanied by the cylinder elongation and appearance of pericentriolar structures, such as rootlet system, basal legs, and basal plate. Centriolegenesis proceeds in both ciliate and nonciliate (with microvilli) cells of the epithelium. It has been proposed that the cell with microvilli represent a transitional stage in differentiation of the ciliary cells.     

Janospira - an Ordovician microfossil in search of a Phylum

Janospira is described from early Ordovician (Arenig) rocks of northern Spitsbergen. It is a curious microfossil, probably calcareous, about 1 mm in length, made up of an initial coil which expands distally into a straight tube, at the same time as producing a narrower tube almost in line with the first but in the opposite direction. Although showing some similarities to Foraminifera, molluscs and polychaetes, there are objections to its inclusion in any of these groups, and it is equally probable that it belongs to an unknown group with a planktic early growth stage.     

Chemical synthesis of a tetradecamer in the deoxyribonucleic acid series

The chemical synthesis of a tetradecadeoxyribonucleotide, d-EtSp(A-T-G-G-A-A-A-C-T-G-C-G-G-C), is described. This oligomer, designated Fragment 4δ, constitutes the 5′-terminus of the plus strand of a projected duplex coding for S-Peptide_2–14 derived from Ribonuclease A. The Fragment was constructed by block condensation via a phosphorothioate anchor. Complications due to inadvertent phosphotriester condensations are discussed. Arguments justifying the sequence selection are presented.