[Early embryo orientation by direction of the cardinal point in natural clutches of two ranidae species inhabiting geographically distant regions]. / Orientatsiia rannikh zarodyshei po napravleniiam stran sveta v estestvennykh kladkakh dvukh vidov ranidae, obitaiushchikh v geograficheski otdalennykh regionakh.

The azimuth (the least angle with the north-south direction) of the first cleavage furrow and anteroposterior axes of neurula was measured on projections of photographs of natural clutches. The azimuth distribution of the craniocaudal axis of Rana dalmatina neurulae in clutches from southern Italy and the first cleavage furrows of R. arvalis embryos in clutches from central Russia proved identical. Both craniocaudal axes and first cleavage furrows were mostly oriented from west to east. The azimuth distribution of the craniocaudal axis of R. arvalis neurulae in clutches subjected to repeated cold shock proved to be random. The causes and mechanisms of predominant orientation of the embryos in natural clutches of frogs are discussed. We propose that magnetic sensitivity is acquired by cytoskeleton elements, most likely microtubules, during reorganization in the course of normal development or due to experimental influences.

[Changes in the receptive field of pigeon tectum neurons subjected to vestibular and acoustic stimulation]. / Izmenenie retseptivnogo polia neironov tektuma golubia pri deistvii vestibuliarnogo i zvukovogo razdrazhitelei

The changes in the receptive fields of neurons in the deep layers of the tectum opticum were studied as induced by labyrinthine and sound stimulation. Variations in the size of the receptive field, the particular direction of sensitive cells movement, duration of the reaction and amount of impulses in it were found. The results obtained and data from the literature allow one to suggest an active role of tectum opticum in the transformation of signals from the retina depending on the kind of information from other sensory systems.