Even without previous ray-treatment the mechanical effectivenes of the filtration ability of lymph-nodes may be reinforced by connective tissue growth around metastatic melanoma cells. On the other hand melanoma cells can pass this filter just because of the possibility to get into the lymph stream by means of wide lymphatics even within the first series of regional lymphatic ganglia. This is true also for passing the marginal lymphatic sinus and subsequent entering the vas efferens of the lymph-node. The therapeutical inferences of these observations are discussed.