Cnidarians display most of the characters considered as milestones of metazoan evolution. Whereas a tissue-level organization was probably already present in the multicellular common ancestor of all animals, the Urmetazoa, the emergence of important animal features such as bilateral symmetry, triploblasty, a polarized nervous system, sense organs (eyes, statocysts), and a (chitinous or calcium-...

Blinded octopuses can readily be taught to discriminate between objects touched provided that these differ in 'roughness'; objects with equally irregular surfaces, differing only in the distribution of irregularities, and objects of similar texture but different shape, are not distinguished. It seems that the animals are incapable of learning to recognize specific patterns of stimulation in the...

This is a book which one could well recommend for those contemplating nursing as a vocation. It is written in a non-technical style which is easy to read but which is not embellished with flourishes of popular appeal. There are numerous clear illustrations. The author progresses from the development of a typical cell to the vertebrates; she discusses genetics, the determination of sex, and the ...

Proneural genes encode basic-helix-loop-helix (bHLH) transcription factors required for neural precursor specification. Recently amos was identified as a new candidate Drosophila proneural gene related to atonal. Having isolated the first specific amos loss-of-function mutations, we show definitively that amos is required to specify the precursors of two classes of olfactory sensilla. Unlike ot...

The hearing organ of the inner ear was the last of the paired sense organs of amniotes to undergo formative evolution. As a mechanical sensory organ, the inner-ear hearing organ's function depends highly on its physical structure. Comparative studies suggest that the hearing organ of the earliest amniote vertebrates was small and simple, but possessed hair cells with a cochlear amplifier mechan...

Our sense organs and our brain operate as an intricate kind of filter which limits and directs the mind’s clairvoyant powers, so that under normal conditions attention is concentrated on just those objects or situations that are of biological importance for the survival of the organism and its species . . . As a rule, it would seem, the ind rejects ideas coming from another ind as the body reje...

The shapes of flowers and their organization into branching systems, called inflorescences, dictate much of plant diversity. Recent studies have identified key regulators in this diversity, revealing that the inflorescence architecture of Solanaceous species depends on sequential and temporal expression of the WUSCHEL-RELATED HOMEOBOX (WOX) gene EVERGREEN (EVG)/ COMPOUND INFLORESCENCE (S) and t...

A hypothesis regarding the development of imitation learning is presented that is rooted in intrinsic motivations. It is derived from a recently proposed form of intrinsically motivated learning (IML) for efficient coding in active perception, wherein an agent learns to perform actions with its sense organs to facilitate efficient encoding of the sensory data. To this end, actions of the sense ...

Among the most intriguing enigmas of the climate system is that on the one hand, the earth’s climate appears to be exquisitely sensitive to relatively minor variations in the distribution of insolation owing to orbital variations, but on the other hand it is in a grosser sense stable, in that its oceans have not frozen over (at least not in the last 500 million years) or boiled away. To this en...

BACKGROUND AND AIMS Models based on the consideration of plant development as the result of source-sink relationships between organs suffer from an inherent lack of quantification of the effect of trophic competition on organ growth processes. The 'common assimilate pool theory' underlying many such models is highly debatable. METHODS Six experiments were carried out in a greenhouse and outdo...