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.
Oxygen consumption in ammocoetes of the lamprey Ichthyomyzon hubbsi Raney.
1. A continuous flow respirometer suitable for measuring oxygen consumption in some small burrowing aquatic animals is described. 
 
2. Rates of oxygen consumption in ammocoetes of the lamprey Ichthyomyzon hubbsi are low, with mean values at 15.5 °C ranging from 38.8 to 97.1 µl/g/h for large (3.44 g) and small (0.14 g) animals respectively. 
 
3. A Q10 of 3.6 was found for medium-size animals (1.18 g) between 3.5 and 22.5 °C. 
 
4. The slope of the logarithmic linear regression relating weight and oxygen consumption was 0.718 at 15.5°C. 
 
5. The rates of oxygen consumption are discussed with respect to the ecology of ammocoetes and compared with those obtained for other lower vertebrates.
Diurnal Periodicity in the Activity of Petromyzon Marinus and the Effects of Chemical Stimulation
Abstract Both the transforming ammocoete and parasitic Petromyzon marinus display an endogenous cyclic activity rhythm. The rhythm is gradually lost in constant conditions of dim light but is re-established by exposing the animal to one or two artificial diurnal light cycles. The period of the endogenous cycle in one larva was 22 hours 58 minutes. Rhythm in the parasite can also be re-established by exposing the animal during a single short period to chemical sensory stimulation produced by the scent of fish. Diurnal rhythm so established was maintained during a period of 5 days at the end of which the observations ceased. Sensory stimulation can function as a “setting” mechanism of the physiological clock. In this instance the setting mechanism is not related to the metabolism of the animal but must have its seat in the central nervous system.