Oxygen consumption in burrowed and unburrowed ammocoetes of Lampetra planeri (Bloch).
Abstract 1. 1. At 15°C, the attainment of a constant rate of oxygen consumption took up to approximately 3 hr in burrowed and 12 hr in unburrowed ammocoetes. 2. 2. The rate in acclimated ammocoetes (mean wet wt. l·34g) burrowed in the light and dark was 41·7 and 40·1 μl/g per hr respectively and in unburrowed animals under the same regimes was 69·0 and 55·7 μl/g per hr. 3. 3. These results clarify conflicting previous recordings and indicate that ammocoetes have a very low metabolic rate.
The Feeding of Ammocœtes.
IN accounts of the Cyclostomata it is generally said that the Ammocœtes larva of the lamprey feeds by means of a current of water caused by the action of its pharyngeal cilia, and that food particles, entangled in mucus, are carried back to the gullet in the same way as in Amphioxus or in an Ascidian (cf. “Encycl. Britt.”, 14th ed., art. Cyclostomata).
Palaeocarpinus (Extinct Betulaceae) from Northwestern China: New Evidence for Paleocene Floristic Continuity between Asia, North America, and Europe
Spiny-bracted fruits of Palaeocarpinus Crane, a genus of Betulaceae previously known only from Europe and North America, have been discovered in the Paleocene of Altai, northwestern China. The fruits are found in association with abundant Corylus-like foliage and staminate catkins containing Corylus-like pollen. Because of problems distinguishing leaves of Corylus from those of extinct betulaceous genera, we place these leaves in the genus Corylites Gardner ex Seward & Holttum. The fruits, staminate catkins, pollen, and leaves from Altai were probably all produced by a single species. Palaeocarpinus orientalis is nearly identical in its morphology to Palaeocarpinus joffrensis from the Paleocene of North America except in the more rounded primary bracts of the associated staminate catkins. The species is less similar to Palaeocarpinus laciniata from the Paleocene of southern England.