The systematics of the Bryozoa (Ectoprocta) found in northern lower Michigan.

Abstract

1. The general systematics of the bryozoa found in the Northern Lower Michgian area was studied for a seond summer. 2. Six species of bryozoa were collected from eighteen localities, which were in the order of greatest abundance first: Plumatella repens, Fredericella sultana, Cristatella mucedo, Paludicella articulata, Plumatella fruticosa, and Plumatella emarginata. 3. The general eclogy of these bryozoa are discussed in general. 4. The first occurrence of Plumatella fruticosa from Cheboygan County is reported here. 5. The problem of distinguishing Plumatella repens from P. emarginata is discussed. 6. The evolution of the bryozoa is speculated upon. A phoronid is probable as being ancestral to the bryozoa. 7. A solution to the problem of the large numbers of floatoblasts present in the plankton of Douglas Lake is offered. 8. The synonomy and world-wide distribution of the bryozoa found in the continental United States is discussed. 9. As a result of measuring natural rates of colony growth at two localities, factors such as predation, physical disturbances, and limiting factors such as available substrate may limit growth. 10. Growth is exponential in the bryozoa studied, that is, unrestricted growth until a factor (s) become limiting. 11. Doubling rates of the polypides of P. repens varied from 3.2 to 4.5 days. 12. There is some evidence that Plumatella fruticosa has a much smaller natural rate of growth than Plumatella repens. 13. A key to the Bryozoa of the Douglas Lake region is included. 14. Plumatella emarginata was found for the first time in an inland stream of Emmet County.