Octopuses are generally characterised by rapid non-asymptotic growth, with high individual variability. However, in situ octopus growth is not well understood. The lack of an ageing method has resulted in the majority of our understanding of octopus growth coming from laboratory studies. Despite not being applicable to cephalopods, Modal Progression Analysis (MPA) of length–frequency data is the most common method for examining in situ octopus growth. Recently, counting growth increments in beaks and vestigial shells, and quantifying lipofuscin in brain tissue, have all shown promise for the ageing octopus. Octopuses generally demonstrate two-phase growth in the laboratory, with physiological changes possibly associated with the switch between an initial rapid exponential phase and a slower power growth phase. Temperature and food ration and quality are key factors influencing the initial growth phase. Temperature, however, does not appear to affect the second phase in any consistent way, perhaps because maturity stage can influence the growth response. There may be basic differences in the mechanisms of octopus muscle growth compared with that of other cephalopods. Furthermore, higher relative maintenance energy expenditure, along with the low energy content of their prey, may account for the relatively slow growth of deep-sea octopuses compared to littoral species.

Senescence is a normal stage of an octopus's life cycle that often occurs before death. Some of the following symptoms typify it: lack of feeding, retraction of skin around the eyes, uncoordinated movement, increased undirected activity, and white unhealing lesions on the body. There is inter- and intraspecific variability. Senescence is not a disease or a result of disease, although diseases can also be a symptom of it. Both males and females go through a senescent stage before dying-the males after mating, the females while brooding eggs and after the eggs hatch. There are many aspects of octopus senescence that have not yet been studied. This study discusses the ecological implications of senescence.

Modern intense ultrafast pulsed lasers generate an electric field of sufficient strength to permit tunnel ionization of the valence electrons in atoms 1 . This process is usually treated as a rapid succession of isolated events, in which the states of the remaining electrons are neglected 2 . Such electronic interactions are predicted to be weak, the exception being recollision excitation and ionization caused by linearly-

The bilateral removal of the carotid bodies and consequent denervation of the carotid sinuses, as a treatment for asthma, provided the opportunity to study the physiological effects of these procedures in the human being. METHODSThe subjects were two hospital patients with long-established bronchial asthma. Their histories and clinical condition have been described elsewhere (Wood, Frankland & Eastcott, 1965 A box bag respirator (Donald & Christie, 1949) was used to administer gas mixtures for periods of up to 4 min each and to record tidal volume and respiratory frequency.The gas mixtures were saturated with water vapour at room temperature and had the following composition: room air, 100 % oxygen, 10 % oxygen in nitrogen, 3 % carbon dioxide in air and 6 % carbon dioxide in air. 10 % oxygen was usually administered twice on each occasion. On some occasions arterial oxygen saturation was recorded with an Atlas ear oximeter which was calibrated against samples of arterial blood analysed by manometric Van Slyke estimations and was accurate to within + 4 %. Arterial blood pressure and pulse rate were measured at frequent intervals by auscultation and palpation respectively or by a Sanborn pressure transducer and recorder through a needle in the brachial artery. The frequency response was accurate from 0.5 to 15 c/s. Passive changes in posture were produced by tilting the subject on an Eve rocker which had been modified to allow a vertical position. Valsalva mannsuvres were performed by the subject blowing against a mercury column. RESULTS Chemoreceptor responsesSubject A. Before operation subject A responded normally by hyperpnoea to breathing 10% oxygen, 3 % C02 and 6% CO2. There was no cyanosis.At operation, both carotid bodies were removed and the adventitia was peeled off for about 2 cm on each side of the carotid bifurcations (Wood et al. 1965). Recovery was uneventful. Two weeks after operation the

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