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| Ball, Ian R.; Hay, David A.. |
| Macquarie Island (54°37'S 158°54'E) has been investigated for the occurrence of freshwater macroturbellarians. Twenty sites were examined but only one species, here ascribed to the genus Minona sensu lato of the Monocelididae, was found and it is described as Minona amnica sp. nov. Its closest taxonomic relationships seem to be with M. istanbulensis Ax from the Black Sea, and M. mica Marcus from Brasil. The new species is unusual in that it occurs throughout the fresh waters of the island even though it is a member of a predominantly marine group. Minona amnica occurs from windswept plateau lakes down to brackish water near the sea and data concerning the distribution and relative abundance of the species in various habitats are presented and discussed. |
| Tipo: Article / Letter to the editor |
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| Ano: 1977 |
URL: http://www.repository.naturalis.nl/record/504339 |
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| Ball, Ian R.. |
| Dugesia gonocephala (Dugès, 1830) and D. polychroa (Schmidt, 1861), collected from the Greek island of Corfu, have been investigated karyologically. The former is a sexual diploid (2n = 16) in which all the chromosomes are metacentric. The latter is a sexual diploid (2n = 8) with one submetacentric and three metacentric chromosome pairs. Within the Dugesia lugubris-polychroa complex seven biotypes are known. The karyotype of D. polychroa from Corfu is most similar to biotype G from the western Mediterranean. However, there are subtle karyological and morphological differences between the two forms and thus the Corfu population is not assigned to biotype G but is considered to have been derived independently from the basic biotype A. Thus it represents an... |
| Tipo: Article / Letter to the editor |
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| Ano: 1979 |
URL: http://www.repository.naturalis.nl/record/503857 |
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| Vries, Elizabeth J. de; Ball, Ian R.. |
| Dugesia gonocephala s.l. is often considered to be a “superspecies” comprising numerous component “microspecies” which are morphologically, karyologically, and reproductively delimited. We have studied populations of D. gonocephala from France, Belgium and The Netherlands and found them to be fairly uniform in respect of most features studied. Nevertheless, discrepancies between them and the “classical” concept of this species as embodied in the literature have raised doubts as to the status and identity of D. gonocephala s. str. A proper understanding of the relationships of the D. gonocephala group can not be obtained without resolution of this problem. |
| Tipo: Article / Letter to the editor |
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| Ano: 1980 |
URL: http://www.repository.naturalis.nl/record/503983 |
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| Ball, Ian R.. |
| Popper’s falsifiability criterion, cast in the form of modus tollens, or ((P > Q). ~Q) > ~P, has often been applied to phylogenetic and cladistic theories. A severe criticism of such application is here examined. Questions concerning the universality, strict or numerical, of the propositions involved are irrelevant, but it is clear nevertheless that some workers have used modus tollens in an inappropriate way. Reliance on it is incorrect if the implicational statement, P > Q, is either a definitional or stochastic conditional. But if it is framed as a causal conditional then a Popperian approach to phylogenetics remains viable, although it is doubtful that this is true also of cladistics, which eschews a causal approach. |
| Tipo: Article / Letter to the editor |
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| Ano: 1982 |
URL: http://www.repository.naturalis.nl/record/504199 |
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| Ball, Ian R.. |
| A primitive freshwater planarian, Eviella hynesae gen. et sp. nov. is described from Australia. It is characterized by its lack of eyes and pigment, possession of caudally branched oviducts, and fully fused testes. Although a primary bursa is absent, its function being taken over by the modified female genital canal, the female copulatory system is posterior to the male system. Despite this maricolan feature, and other similarities with primitive southern hemisphere freshwater planarians that have been classified in the Maricola, the present species is placed in the family Dugesiidae of the Paludicola. Evidence from its sensory organs suggests that it belongs on the main evolutionary line from which the majority of Australasian freshwater planarians have... |
| Tipo: Article / Letter to the editor |
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| Ano: 1977 |
URL: http://www.repository.naturalis.nl/record/504587 |
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| Ball, Ian R.. |
| The type material of Colombian species of freshwater triclads (Fuhrmann, 1914) is revised and the original descriptions corrected and amplified. Planaria polyorchis is conspecific with Dugesia festai (Borelli). Planaria longistriata is a typical Girardia species of the Dugesia (Girardia) tigrina group, a group widespread in North and South America. Planaria paramensis and P. cameliae belong to a group of Dugesia species characterized particularly by their dorsal testes, and exemplified by a number of species in and around the Caribbean region. |
| Tipo: Article / Letter to the editor |
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| Ano: 1980 |
URL: http://www.repository.naturalis.nl/record/504178 |
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| Ball, Ian R.; Vinh-Hao, Tran Thi. |
| Three new freshwater triclads are described from Tasmanian lakes. Two of these represent the first records of the genus Spathula in Tasmania and the third belongs to the endemic genus Romankenkius. The taxonomic affinities of the species are discussed and keys to all the Tasmanian genera and species are provided. These keys are to be regarded as provisional since it is likely that there remain many planarian species to be discovered and described from Tasmania. |
| Tipo: Article / Letter to the editor |
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| Ano: 1979 |
URL: http://www.repository.naturalis.nl/record/504467 |
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| Ball, Ian R.; Gourbault, Nicole. |
| The amphiatlantic distribution of the genus Planaria is incompatible with our current hypothesis of the historical biogeography of freshwater planarians. New anatomical studies suggest the possibility that the genus is not strictly monophyletic; new karyological data are strongly corroborative of that conclusion. The karyotypes of the American species of Planaria are almost identical with those of many other North American Planariidae and quite distinct from that of the European species. These findings are inconsistent with the hypothesis that the species of Planaria form a strictly monophyletic group. Therefore the amphiatlantic disjunction is apparent, not real, and the earlier biogeographical hypothesis is protected from one potential falsifier. |
| Tipo: Article / Letter to the editor |
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| Ano: 1978 |
URL: http://www.repository.naturalis.nl/record/504479 |
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