148 
lilCTTAEI) ASSIIETON. 
cliiniiiutiuu of tlic length of the bliistodenn occuiTing at lliat 
moment. 'J’his is s:iid to hiive been so in two eggs wliicli 
were kept under observation for and 3j lionrs respectively. 
Piitterson objects to some experiments made by myself in 
189G (‘ i’roc. Hoy. Soc./ vol. lx, 1896) with a view to testing 
Duval’s theory of concrescence on chicks, thus: (1) They 
were ])erformed after concrescence had occurred, which is a 
valid objection if Patterson’s contention thnt all this occiii's 
before laying is correct. (2) The cells may have flowed round 
the bristle held in place by vitelline membrane and y<dk. 
'i’liis objection, which, of course, is irrelevant in this par- 
ticular case if the first holds good, must be considered as a 
general objection to the use of bristles for such purposes. 
'I’he bristle, it may be said, makes a perfectly unmistakable 
landniark, which cannot be said of injuries by cauterisation. 
The objection is one which has naturally occurred to me, 
but I am convinced that the objection is groundless for the 
following reasons : 
In the nutnerous experiments made upon chick and frogs’ 
eggs with sable hairs, I have never seen any evidence that 
cells can flow round the hair. 
The results would not be so constant if there were any 
flowing of cells round the bristle. 
If cells could move so easily as to avoid a bristle without 
making any visible sign of disturbance, they would be 
affected by the force of gravity and become displaced when 
eggs are not in their normal position. 'This is not the case. 
A fully segmented egg of liana temporaria maybe held 
down at an angle of 90° to its normal position without affect- 
ing the normal relation of its cells to one another. When 
there has been a very severe drag upon the bristle on account 
of some excessive stress in tin vgg, due to some displacement 
with refei’ence to the vitelline membrane, tmd tin tdtempt has 
lieen made by the cells to flow round the bristle, the elfect is 
obvious, and is seen tis ti bay or wrinkle which is quite absent 
from properly ])erformed experiments of the kind, and indi- 
cates oidy an attempt of a soft tissue to swing round the 
