Polyp Colony Research Articles

A new record ofCraspedacusta sowerbii(Cnidaria: Limnomedusae) from southern Africa

The northern hemisphere Craspedacusta sowerbii has been recorded recently from temperate regions of South Africa. Its introduction to southern Africa is thought to have occurred in the 1940s, when a number of exotic species were introduced, associated with man's interference in river catchments. A new record from Theewaterskloof Dam, Cape Province, suggests that its spread is being facilitated by inter-basin translocation of the polyp stage. Histological analysis of the gonads of medusae from Theewaterskloof impoundment showed that they were all females, supporting the hypothesis that only one sex of medusa is budded from any one polyp colony.

Hydroid generation and developmental history ofEucheilota maculata (Thecata — Leptomedusae). With a contribution to the methods of culturing marine hydroids

Polyps and medusae differ in regard to habitats, evolution, and morphological structures. In order to replace the former taxonomic systems which deal with polyp and medusa generations separately, by a single valid classification including both generations, knowledge of all essential life history phases is necessary. Modern methods of culturing marine hydroids are outlined briefly. Successful culturing provides the means to link formerly unidentified polyps or medusae with one another. The present paper is concerned with the hydroidEucheilota maculata Hartlaub, the medusa of which is common in the southern North Sea. The polyps formerly unknown have been reared from fertilized eggs of the medusae. They were raised to full size, formed colonies, and produced gonangia and medusae. Thus the morphology of the single polyp, the polyp colony, and of the young medusa could be investigated in detail. The nematocyst equipment of the two generations and of all developmental stages is described as well as the number of chromosomes. The systematic position of the genusEucheilota is discussed and the diagnosis of the speciesE. maculata, including the two generations, given.

Acquisitions of the Natural History Museum

A SERIES of microscope preparations showing all the early stages in the life history of the graptolite Climacograptus has been presented to the Department of Geology of the Natural History Museum by the Sedgwick Museum, Cambridge. The preparations were made by Mr. Ian Cox from material which he collected from rocks of Ordovician age in Akpatok Island, Ungava Bay, Northern Territory, Canada. Graptolites occur in the oldest fossiliferous rocks, and are organisms of unknown relationships, but generally supposed zoologically to resemble the living sea-firs, or sertularians?minute colonies of polyps encased in a horny skeleton. In the material from Akpatok Island, the original horny skeleton is preserved in a matrix of limestone, which can be dissolved and the skeleton extracted entire. The minutest structure and ornament of the early chambers, or thecæ, are visible, and the order and manner of budding of new thecæ can be clearly determined. Miss K. B. Macvicar has presented the extensive herbarium of her brother, Dr. Symers M. Macvicar, to the Department of Botany. Dr. Macvicar was the recognised British authority on Hepaticæ and was the author of the standard systematic account of them,?The Student?s Handbook of British Hepatics?. The herbarium is very rich in British and Continental species, and these are the more valuable because they are the basis of the descriptions and comparisons in the?Handbook?. Dr. Macvicar was a medical man whose home was at Acharacle, Argyll, and in his travels in western Scotland accumulated an unrivalled representation of the flora, particularly of the less frequented parts of Argyll and Inverness. The herbarium contains about 18,000 specimens (that is, labels) and, as well as hepatics and flowering plants, contains mosses, seaweeds, and lichens. Mr. A. H. G. Alston, assistant keeper in the department, has just returned from western Greek Macedonia, where, in company with Mr. N. Y. Sandwith, of the Kew Herbarium, he spent six weeks. He collected about 1200 specimens, chiefly flowering plants. These are of interest because the area along the Albanian frontier has been visited previously only by a Czechoslovakian collector? moreover, the districts visited overlap to some extent those from which some plants were obtained by the department during the War.