The origin of marine invertebrate larvae has been an area of controversy in developmental evolution for over a century. Here, we address the question of whether a pelagic “larval” or benthic “adult” morphology originated first in metazoan lineages by testing the hypothesis that particular gene co-option patterns will be associated with the origin of feeding, indirect developing larval forms. Empirical evidence bearing on this hypothesis is derivable from gene expression studies of the sea urchin larval gut of two closely related (...) but differently developing congenerics, Heliocidaris tuberculata (feeding indirect-developing larva) and H. erythrogramma (nonfeeding direct developer), given two subsidiary hypotheses. (1) If larval gut gene expression in H. tuberculata was co-opted from an ancestral adult expression pattern, then the gut expression pattern will remain in adult H. erythrogramma despite its direct development. (2) Genes expressed in the larval gut of H. tuberculata will not have a coordinated expression pattern in H. erythrogramma larvae due to loss of a functional gut. Five structural genes expressed in the invaginating archenteron of H. tuberculata during gastrulation exhibit substantially different expression patterns in H. erythrogramma with only one remaining endoderm specific. Expression of these genes in the adult of H. erythrogramma and larval gut of H. tuberculata, but not in H. erythrogramma larval endoderm, supports the hypothesis that they first played roles in the formation of adult structures and were subsequently recruited into larval ontogeny during the origin and evolution of feeding planktotrophic deuterostome larvae. (shrink)

Reductionism and holism, that is, antireductionism, are two of the prevailing paradigms within the philosophy of biology. Reductionists strive to understand biological phenomena by reducing them to a series of levels of complexity with each lower level forming the foundation for the subsequent level, by mapping such biological phenomena inasmuch as possible to the principal phenomena within the fundamental sciences of chemistry and physics. In this way, complex phenomena can be reduced to assemblages of more elementary explananda. Holism, in counterpart, (...) claims that there independently exist phenomena arising from ordered levels of complexity that have intrinsic causal power and cannot be reduced in this way. When dealing with the nature of biology and its unique foundations of essentialism, determinism and ethics, the pedagogical lens through which these foundations are conveyed to learners could provide a limited perspective if only the reductive approach is followed as it would not sensitise learners to the true complexity of the phenomenon of life and the study thereof, and it is the purpose of this article to frame the reductionist–antireductionist debate in order to illustrate this.Contribution: This article contributes new knowledge to the field of the philosophy of science; more specifically, the philosophy of biology by critically evaluating the pervasive dialectic between the theoretical frameworks of reductionism and antireductionism and alluding to the pedagogical consequences thereof. (shrink)

Many years ago Wilamowitz desiderated a systematic collection of the texts which relate to the different types of poetry composed by the great lyric poets of Greece. He hoped that if we could only crystallize our admittedly scanty information about the characteristics of, say, the Paean or the Dirge, we might be able to reach a slightly better understanding than we have now of the formal structure and artistic design of the poems and fragments which have come down to us (...) under these titles. Indeed, this kind of knowledge is very important. (shrink)

This is a clear assessment of Hume's theories of the self and personal identity, including his famous Treatise on Human Nature . Pitson provides a critical exploration of his thinking, also examining the continuing relevance of Hume's theories for contemporary philosophy and relating it to his broader reflections on human nature itself. Divided into two parts, Pitson's study follows Hume's important distinction between two aspects of personal identity: the "mental" and the "agency". The first part discusses Hume's conception of the (...) mind as a "bundle" or "system" of perceptions and explores Hume's position on the traditional mind/body problem. In the second part Pitson examines a range of topics including Hume's treatment of character, the relationship between human and animal nature, and the nature of agency. (shrink)

Both the author and the date of this five-volume poem, the first Western document to link the houses of the zodiac with the course of human affairs, are uncertain. The author's name may be Marcus Manilius, or Manlius, or Mallius, and the latest datable event mentioned in the books themselves is the disastrous defeat of Varus' Roman legions by the German tribes in 9 CE. The writing shows knowledge of the work of Lucretius, but the work is not referred to (...) by any subsequent writer, suggesting that it was never widely disseminated. A manuscript was rediscovered by Poggio Bracciolini in 1416 or 1417, and editions were produced by Scaliger and Bentley, but this immensely erudite edition of 1903–1930 by the scholar and poet A. E. Housman is regarded as authoritative. Volume 2 describes the signs of the zodiac, their characteristics and their subdivisions. (shrink)

Epitome V (1621), and consisted of matching an element of area to an element of time, where each was mathematically determined. His treatment of the area depended solely on the geometry of Euclid's Elements, involving only straight-line and circle propositions – so we have to account for his deliberate avoidance of the sophisticated conic-geometry associated with Apollonius. We show also how his proof could have been made watertight according to modern standards, using methods that lay entirely within his power. The (...) greatest innovation, however, occurred in Kepler's fresh formulation of the measure of time. We trace this concept in relation to early astronomy and conclude that Kepler's treatment unexpectedly entailed the assumption that time varied nonuniformly; meanwhile, a geometrical measure provided the independent variable. Even more surprisingly, this approach turns out to be entirely sound when assessed in present-day terms. Kepler himself attributed the cause of the motion of a single planet around the Sun to a set of `physical' suppositions which represented his religious as well as his Copernican convictions; and we have pared to a minimum – down to four – the number he actually required to achieve this. In the Appendix we use modern mathematics to emphasize the simplicity, both geometrical and kinematical, that objectively characterizes the Sun-focused ellipse as an orbit. Meanwhile we highlight the subjective simplicity of Kepler's own techniques (most of them extremely traditional, some newly created). These two approaches complement each other to account for his success. (shrink)