99 



BuRCKHARDT (5), foi' sheep, swine and male deer by Profe (12), for 

 the white rat by Henneberg (6), for the guinea-pig and mouse by 

 Schickerle (14), for the Cetacea by Kükenthal (11), and for Mar- 

 supials by Hennig (7) and Bresslau (4). A nriost excellent review 

 of the work done up to 1897 is given by Bonnet (3). Whether the 

 supernumeraries described by these authors are in all cases homologous 

 to the structures in man described by Hugo Schmidt is doubtful. It 

 is more probable that they are homologous to persistent supernumer- 

 aries in man, since it is by no means certain that these persistent 

 human supernumeraries are the survivors of the temporary Anlagen of 

 Hugo Schmidt. 



The following paper contains the evidence given by two additional 

 human embryos, the opportunity of examining which I owe to the 

 kindness of Professor Keibel. I wish here to express my thanks to 

 Professor Keibel for the use of his material and for his many valuable 

 suggestions, and also to Geh. Hofrat Professor Wiedersheim in whose 

 laboratory the work has been done. 



Description of the Embryos. 



In Table I are arranged in the order of their size, and therefore 

 of their approximate age, Professor Keibel's two embryos (named 

 Piper I and Piper II), together with those of Schmidt, Schmitt and 

 Strahl mentioned above and also those of Hirschland (8) and the 

 famous Kallius - embryo (10) on which the mammary line was first 

 seen in man. The fact that Schmidt used the hindbrain-coccyx 

 ("Hinterhaupt -Steißbein") standard in measuring his embryos while 

 Schmitt and Kallius used the forebrain - coccyx ("Kopf- Steißbein") 

 dimension and Strahl and Hirschland do not specify which they 

 did use, makes the arrangement of such a table somewhat problema- 

 tical. 



Piper II S- This embryo was preserved in chrom-aceto-sublimate, 

 stained with borax - carmine, embedded in paraffine and cut into 877 

 cross-sections of 15 /ii each. Its greatest length (from forebrain to 

 coccyx) measures about 15,5 mm and from hind -brain to coccyx, 

 14,5 mm. It comes between Fig. 19 and Fig. 20 according to His' 

 table (9) and is therefore approximately 37 days old. The epithelium 

 was fairly well preserved except for a small area on the right side above 

 the leg. Two wax models were reconstructed from the sections, one 

 of the whole embryo (enlarged 16^/3 times, every fourth section being 

 used), and the other of that region alone showing the epithelial struc- 

 tures in question (enlarged 66^/3 times, every section being used). 



