152 
RICHARD ASSHRTON. 
this with a section of “ an nninjnred blnstoderm at a corre- 
sponding stage/’ and to note that “ the entoderm in this region 
is very thick (see tig. 37). It is clear, tlierefore, that while such 
an operation destroys most of tlie cells that are to give rise to 
the entoderm, yet the postei-ior margin is still capable of 
forming a rounded dorsal lip.” I venture to submit that it 
is perfectly impossible to deduce any such conclusion from 
the figures given. 
Fig. G6 represents a magnification of 125 diametei's, and 
the point of injury is about 3.| in. from the dorsal lip. Fig. 
37 is magnified 245 times, but as the whole section measures 
less than 5 in. it cannot contain the required spot. There is, 
however, another figure of the same section, fig. 35, which is 
magnified 107 times. If we examine the region 2| in. or 
even 2 in. to the left of the edge of the blastoderm, we fail 
to see any greater accumulation of entoderm cells in the 
nninjured than in the injured one. 
Possibly I may have made a mistake in my interpretation 
of his fig. 66, and the number “ 66 ” is at the anterior end 
and not the posterior end as I assumed. In that case I am 
at a loss to find either the cells which have been injured or 
the deficiency in the entoderm I'eferred to. If the latter is 
indicated by the clearer spot near a letter “ z ” (of the figure 
above) then the corresponding spot in fig. 35 or 37 is just 
as devoid of entoderm as in 66. Or if, as he seems to 
suggest, we are to contrast fig. 67 with a part still further to 
the left in fig. 35, I fail to see innch difference in the con- 
dition of the “ entoderm.” On this latter assumption, the 
spot labelled “op” is presumably the “break” in the 
vitelline membrane made by the operating needle, from which 
the free edge has curled away forwards. Since there is not 
a- ti'ace of vitelline membrane shown, the photograph fails 
to strengthen the argument in the text. 
I think it must be admitted that the author has not been 
successful here in his attempt at demonstration. 
Exp. II. (Operation 35| hours after fertilisation. Subse- 
quent incubation 49 hours.) 
