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in Scyllium. But the first sections, which disclosed the yolk-emulsion 
in the embryonic gut, also revealed something far more astonishing. 
Scattered liberally in this emulsion were numbers of what looked like 
remains of nuclei or of chromatin of cells. 
When these and the emulsion were followed back to their place 
of origin, and when this was examined in a number of embryos of 
older stages, it was easily made out that these things, i. e. the emul- 
sion and the nuclear structures, had come from the merocytes at the 
place, where the embryonic gut was incomplete, i. e. where it opened 
on to the yolk-sac, or, as I prefer to put it, where its ventral wall 
was made up of part of the larval gut, the merocytes. 
At this point there was a mass of emulsion, small yolk - plates, 
and nuclear elements in the lumen of the gut, and further forwards 
there was nothing. Here, too, the merocytes formed one or two little 
hillocks projecting into the cavity of the gut. The components of these 
hillocks were filled with yolk in various stages of disintegration. 
What has just been described could be verified in every embryo 
of 9 mm and upwards examined and practically in every section, in 
the region where the gut is still open to the surface of the yolk-sac ‘). 
The exact details of what is taking place can be better made out 
and described from careful drawings of all the things seen in a favour- 
able section. 
Such a sketch, if it be made to represent the finer details, is of 
too elaborate a character for reproduction by the “process” method, 
and for this reason the publication of such pictures must be deferred 
for another occasion. 
One such drawing from an embryo?) of 11,5 mm now lies before me, 
and an endeavour may be made to describe what it depicts. Resting on 
the yolk the gut, with a wide lumen, is seen in the transverse section. 
From the nature of the epithelial lining it is clear, that the dorsal wall 
of the gut, the whole of the actual right lateral wall, and about half 
of the actual left lateral wall belong to the permanent alimentary 
canal. The points, where the ingrowths previously mentioned, will take 
place are somewhat sharply defined. The whole of the ventral wall 
and a portion of the left lateral wall are formed by merocytes, and 
1) The intensity of the process varies considerably. Thus, the pro- 
liferation of yolk-filled cells is usually very slight, before the embryo is 
11 mm long, then there ensues a period of rapid formation and prolifer- 
ation, and, finally in older embryos (14 mm and upwards) it again be- 
comes abated; but the process is always the same in kind, though its 
degree may vary. 
