METANEPHRIC ANLAGE OF CHICK 
413 
MATERIAL AND METHOD 
The material upon which this investigation is based consists 
for the most part of grafts of the metanephric anlage isolated 
from chick embryos at a stage of seven days’ incubation and 
grown on the allantois of seven-day chick embryos. The eggs 
were opened under aseptic conditions and the embryos laid out 
in sterilized glass dishes. An opening was made along the 
ventral midline, and the heart, liver, and digestive tract were 
cut away. The glands and ducts of the urogenital system were 
thus exposed. Before attempting to isolate the metanephric 
anlage, it was found most convenient to remove the whole urogeni¬ 
tal system from the body cavity and to transfer it to a watch- 
glass, disturbing the general relations as little as possible. Thus 
the metanephric anlage in relation to the various parts of the 
urogenital system could more readily be seen and dissected out. 
The metanephric anlage was separated out by cutting the ure¬ 
teric diverticulum just above its entrance into the cloaca and by 
teasing the anlage apart from its connections with other tissues. 
The organ at this stage is about 1 mm. in length. Care was 
taken to keep the tissues well moistened with blood plasma dur¬ 
ing the process of isolation. Text figure A is a diagram of the 
separated metanephros as it appeared under the binocular 
microscope. The figure shows that the metanephric diverticu¬ 
lum has already begun to branch. The branches are arranged 
in two groups, a cranial, larger group, and a caudal, smaller 
group, joined together by an unbranched portion of the ureteric 
channel. 
The eggs used as hosts for the grafts were likewise at a stage 
of seven days’ incubation. At this time the allantois is well 
supplied with a vascular net and conditions are extremely 
favorable for the establishment of vascular connections be¬ 
tween the graft and the host. The method of procedure in the 
grafting was that used and described by Danchakoff (T6). 
A window was sawed out over a large allantoic vessel, upon which 
the metanephric anlage was carefully laid. In some cases the 
entire metanephric anlage was grafted, in other cases only its 
