[Studies on blood morphology in the European eel (Anguilla anguilla). I. Erythrocytes and their developmental stages].

By means of heart tapping we produced a larger loss of blood in the European eel, Anguilla anguilla. This resulted in enriching the peripheric blood with erythroblasts and proerythrocytes. By panoptic staining erythroblasts, proerythrocytes and mature erythrocytes could be prepared and described. By the aid of supravital staining it was possible to detect mitochondria and Substantia granulofilamentosa in all stages of development. Phase contrast observations proved that the erythrocytes of Anguilla anguilla do not possess any locomotion ability. Cytochemical investigations showed that the erythrocytes weakly or very weakly react to acid phosphatases, lipids and ribonucleic acids and positively to unspecific esterases. The artificially produced loss of blood and the following continuous extraction of blood gave indications of how rapidly the erythrocytes form and how much time their maturing takes. 48 hours after tapping erythroblasts appeared in large amounts. The number of proerythrocytes increased 24 hours later. The transformation of proerythrocytes into mature erythrocytes does not take more than 48 hours. The loss of erythrocytes caused by heart tapping is already compensated six days later by new growth. During this investigation division processes in erythrocytes were observed. These are endomitotic or amitotic division or mitotic ones which are very rarely observed.