560 



other leucocytes encountered, and there were none outside the thymus 

 within the mesoblast, as is invariably the case in slightly older embryos. 

 The remaining cells of the placode were columnar. In another embryo 

 of 18 mm three well marked leucocytes were detected within a single 

 transverse section of the thymus-epithelium, and there were also two 

 cells in the act of taking on leucocytic characters. In the fourth 

 section in front of the one just mentioned (which lay about the middle 

 of the thymus -element) there was also a single leucocyte to be seen 

 lying in the mesoblast some distance from the thymus. In all the 

 sections, with the exception of a very few leucocytes and cells be- 

 coming such in each, all the rest were epithelial cells. 



(Schluß folgt.) 



Berichtigung. 



Aus Versehen ist in dem Aufsatz von ß. Burckhakdt (No. 20/21) die Schwanz- 

 flosse von Laemargus (Fig. 2) in umgekehrter Lage und die Dorsalflosse einer Centrina 

 (Fig. 4) lim einen rechten Winkel verschoben, abgebildet worden. 



Fig. 2. 



Fig. 4. 



Abgeschlossen am 21. December 1900. 



Krommannsche Buchdruckorei (Hermann Fohle) in Jena. 



