Styles of Reasoning in Early to mid-Victorian Life Research: Analysis:Synthesis and Palaetiology

To better understand the work of pre-Darwinian British life researchers in their own right, this paper discusses two different styles of reasoning. On the one hand there was analysis:synthesis, where an organism was disintegrated into its constituent parts and then reintegrated into a whole; on the other hand there was palaetiology, the historicist depiction of the progressive specialization of an organism. This paper shows how each style allowed for development, but showed it as moving in opposite directions. In analysis:synthesis, development proceeded centripetally, through the fusion of parts. Meanwhile in palaetiology, development moved centrifugally, through the ramifying specialization of an initially simple substance. I first examine a community of analytically oriented British life researchers, exemplified by Richard Owen, and certain technical questions they considered important. These involved the neurosciences, embryology, and reproduction and regeneration. The paper then looks at a new generation of British palaetiologists, exemplified by W.B. Carpenter and T.H. Huxley, who succeeded at portraying analysts’ questions as irrelevant. The link between styles of reasoning and physical sites is also explored. Analysts favored museums, which facilitated the examination and display of unchanging marine organisms while providing a power base for analysts. I suggest that palaetiologists were helped by vivaria, which included marine aquaria and Wardian cases. As they became popular in the early 1850s, vivaria provided palaetiologists with a different kind of living and changing evidence. Forms of evidence, how they were preserved and examined, and career options all reinforced each other: social and epistemic factors thus merged.     

Seed colour loci, homoeology and linkage groups of the C genome chromosomes revealed in Brassica rapa-B. oleracea monosomic alien addition lines

Background and Aims

Brassica rapa and B. oleracea are the progenitors of oilseed rape B. napus. The addition of each chromosome of B. oleracea to the chromosome complement of B. rapa results in a series of monosomic alien addition lines (MAALs). Analysis of MAALs determines which B. oleracea chromosomes carry genes controlling specific phenotypic traits, such as seed colour. Yellow-seeded oilseed rape is a desirable breeding goal both for food and livestock feed end-uses that relate to oil, protein and fibre contents. The aims of this study included developing a missing MAAL to complement an available series, for studies on seed colour control, chromosome homoeology and assignment of linkage groups to B. oleracea chromosomes.

Methods

A new batch of B. rapa–B. oleracea aneuploids was produced to generate the missing MAAL. Seed colour and other plant morphological features relevant to differentiation of MAALs were recorded. For chromosome characterization, Snow''s carmine, fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) were used.

Key Results

The final MAAL was developed. Morphological traits that differentiated the MAALs comprised cotyledon number, leaf morphology, flower colour and seed colour. Seed colour was controlled by major genes on two B. oleracea chromosomes and minor genes on five other chromosomes of this species. Homoeologous pairing was largely between chromosomes with similar centromeric positions. FISH, GISH and a parallel microsatellite marker analysis defined the chromosomes in terms of their linkage groups.

Conclusions

A complete set of MAALs is now available for genetic, genomic, evolutionary and breeding perspectives. Defining chromosomes that carry specific genes, physical localization of DNA markers and access to established genetic linkage maps contribute to the integration of these approaches, manifested in the confirmed correspondence of linkage groups with specific chromosomes. Applications include marker-assisted selection and breeding for yellow seeds.