348 V. Graber 
die Behandlung der in Rede stehenden Frage. Die Hauptpunkte 
seiner Darlegung, die ich hinsichtlich ihrer Bedeutung später wür- 
digen werde, sind nach dem Originale folgende. 
Er beschreibt zunächst pag. 238 die erste Formdifferenzirung 
des im Ganzen schildförmigen Keimstreifs. »The almond-shaped 
thickening is soon divided into two tolerably well marked regions 
by the enlargement of the head end (vgl. den Holzschnitt Fig. 2 7). 
The narrower portion of the germinal band (ZZ) increases some what 
in length and the abdominal end becomes more broadly rounded. 
With the further growth of the embryo the head lobes (Holz- 
schnitt Fig. 3 47) increase rapidly in breadth, the ectoderm at the 
lateral edges becomes thicker, and the posterior portion of the em- 
bryo becomes spatulate in form with the enlarged part of the spa- 
tula forming the tip. There appears a depression in the middle of 
the forehead, which helps to make more conspicuous the bilateral 
symmetry of the head region (Holzschnitt Fig. 3 7)... Almost 
simultaneously . . . two lateral folds (Fig. 3 @ und 38) are for- 
med in the spatulate portion of the embryo, which. . . serve re- 
spectively to mark off the maxillary ([Kiefer-] Fig. 3 JZ) and tho- 
racic (Brust-) regions (Fig. 3 ZZZ). The general shape of the folds 
(Fig. 3 fc) may be compared to... Arabic numeral 3 for the 
right fold... The folds are thickest (wulstartig?) and most sharply 
defined in the maxillary region... The thickened (wulstartigen) 
outer edges of the head fold are at this time continuous behind with 
the outer edges of the germinal band, but they gradually grow 
in towards the median line and are at the same time bent forward 
(Holzschnitt Fig. 4 y) toward the region of the future mouth .. . 
The anterior ends of the maxillary folds (Fig. 3 und 4 #) fuse and 
... forms a transverse elevation extending entirely across the embryo 
behind the cephalic region, forming the anterior limit of the maxil- 
lary region.« 
Weiter heiBt es dann pag. 239: »The maxillary and tho- 
racie constrictions (Fig. 4 5b, c) have becomes more sharply de- 
fined, since the folds have travelled to, and now form the edges 
of the embryo, but the strictly abdominal region has not kept pace 
in its growth with the anterior regions. The embryo is now 
composed of four well markedregions: cephalic (Fig. 4 J), 
maxillary (JZ), thoracic (ZII) and abdominal.« Ayers fährt 
dann fort: »There (nämlich in der Kiefer- und Brustregion) are gra- 
dually raised from the surface five pairs of protuberances 
