2 Ethel Nicholson Browne 
white hydras form perfect grafts with normal green hydras and the 
two parts remain distinct in color. 
In all my experiments, I used for operation a small watch glass 
coated over with paraffine on the bottom and filled with spring 
water. ‘The operations were all done under a binocular microscope 
which has the advantage of giving considerable enlargement and 
plenty of working distance. After operation, the animals were 
kept in watch glasses filled with either spring water or aquarium 
water, renewed daily. 
Part I 
GRAFTS TO PRODUCE A NEW HYDRANTH FROM THE STOCK 
The object of this series of experiments was to determine, first, 
what tissue when grafted into the body of a normal hydra would 
cause a new head to regenerate in the region of the graft; and, 
secondly, in what region of the stock the graft must be made in 
order that the new hydranth develop. ‘To test these questions, 
material was taken from various regions of the body and grafted 
at different levels along the bodies of other hydras. All these 
experiments were done with Hydra viridis as both graft and stock. 
Group A 
Tentacle with Peristome at Base as Graft 
For operation in the present group of experiments, two hydras 
were put into the paraffine-coated watch glass and one was cut 
just below the circle of tentacles. ‘This circlet was cut in one 
radius so that the tentacles extended out from the peristome in a 
straight line or slight curve. From this line of tentacles [ cut off 
one, being careful to leave some peristome tissue attached at its 
base. As quickly as possible I made a small transverse slit in the 
body wall of the other hydra with a small scalpel or sharpened 
needle, and inserted the prepared tentacle into this slit by means 
of a needle. If the operation was successful, the raw surfaces 
healed so that after a few hours there resulted a perfectly normal 
hydra with the exception of a tentacle projecting from some part 
