[Development of telencephalon in Agapornis roseicollis Vieillot (Psittacidae) and its relationship to the evolution of the telencephalon in vertebrates]. / Die Entwicklung des Telencephalons von Agapornis roseicollis Vieillot (Psittacidae) und deren Beziehung zur Evolution des Telencephalons der Vertebraten.

1. The cerebral anlage of Agapornis roseicollis was investigated in serially cut slices during the developmental stages before hatching (day 3-day 20) by light microscopical quantitative and qualitative methods. 2. During earlier stages of development, the brain anlage is divided in three dorsally and four ventrally situated, longitudinally oriented matrix zones (D1-D3, V1-V4 according to Kuhlenbeck). In this developing system, mainly the lateral part of the telencephalic wall including its dorsal extension is considered to establish special importance for the further ontogenetic development. 3. The quite simple structure of the epistriatum in Reptils occurs as the neo-hyperstriatum-complex in Birds; likewise, deriving from the neocortex primitivus in Reptils, in Mammalia this part obviously develops to the more and more expanding neocortex as can be followed from lower mammalia species up to the highly developed Primates. According to the first main criterion of Remane, the homology of these parts of the brain in different vertebrates is most evident because these brain parts occupy exactly the same position in the brain anlage of early embryonal stages. 4. In Reptils, the neocortex primitivus appears as the last during ontogenetic development. Likewise in Birds, the neohyperstriatum-complex that is homologeous to the neocortex in Mammalia, differentiates during the final stages. These facts again emphasize the homology of these structures. 5. Further evidence for homology is obtained by the observation that in Agapornides the primordium of the neo-hyperstriatumcomplex contains migrating matrix cells columns, which also in Mammalia arrange into the same manner. Moreover, the transient and heterochronuous occurrence of cell layers at the outer surface of the brain anlage reminds to the development of palaeocortex and neocortex in Reptils and Mammalia. 6. From the point of view of evolution biology, the process of the progressive evolution is considered to be based on the step by step addition of tiny new structure-function-units to the already present morphology going along with a full structural and functional integration of the added, thus to achive the new quality. This so-called "Additive Morphogenesis" was effective during millions of years, consisting of such microevolutionary processes, and finally caused the "Gestaltungswandel", the ever changing evolving variety of bodily forms (and functions) that is recapitulated during individual species ontogenesis.

[Experimental investigations into the transplantation of one telencephalon hemisphere of ambystoma mexicanum during postembryonal period]. / Experimentelle Untersuchungen zur Transplantation einer Endhirnhemisphäre vonAmbystoma mexicanum während der Postembryonalperiode.

1. In 52 experimental animals (Ambystoma mexicanum) with a body length of 7.5-8.5 cm (including tail) the right telencephalon hemisphere was extirpated and substituted by transplantation of a hemisphere which was taken from an animal of the same bodylength. The heads of all experimental animals were cut in horizontal serial-sections. The result of the transplantation was compared with control animals (resection of one hemisphere without transplantation). 2. After transplantation marked degenerative changes occur in the transplanted hemisphere, but large parts of the matrix regions of the transplant remain intact. Moreover, differentiated brain tissue could be demonstrated at every stage. From the 4th day after transplantation numerous mitoses were found in the transplanted matrix tissue, which lead to an increase in the mass of the parts of the transplant that have remained intact. 3. On the 35th day after operation the transplant is in contact with the regenerating N. olfactorius for the first time. Between the 120th and the 160th day after operation the transplant reaches approximately the size of a normal hemisphere but the shape of the transplanted hemisphere remains very irregular even on the 450th day after operation. 4. By planimetrical investigation of the hemisphere cuts in experimentation and control animals and by statistic evaluation of measurements it could be proved that inAmbystoma mexicanum the resected hemisphere can be replaced by hemisphere-homotransplantation to a great extent during the postembryonal period.