124 Cc. V. MORRILL 
tibia was removed with the foot. Spelerpes ruber was used for 
these experiments. The results were, regeneration of the distal 
end of the tibia, a new foot and a new fibular element. The 
latter was usually incomplete but in one case it almost completed 
itself proximally, that is, reaching the femoral epiphysis. As 
in the present experiments there was no tendency to regener- 
ate from the femur. Wendelstadt, in his later paper (’04) 
states that the experiments of Reed confirm his general conclusion 
that wounding of the skeletal elements is necessary for regenera- 
tion. The experiments described in the present paper show that 
this conclusion is too sweeping. It is true that if one bone only 
(fibula or radius) is removed (Wendelstadt, Reed and the writer) 
or if the proximal parts of two bones are removed (Wendelstadt) 
no regeneration occurs from the uninjured epiphysis of the femur 
(or humerus). In the first case, the pressure of the remaining 
bone against the joint surface of the femur (or humerus) and the 
tarsals (or carpals), that is the presence of a functional joint may 
inhibit regeneration from these points. In the second case the 
new growth centripetally from the remaining injured bones, 
which is always more rapid than from uninjured ones, may make 
up the deficiency in time to check any tendency to regenerate 
from the epiphysis of the humerus. Shortening .of the limb 
which must occur in this case would also be a factor. These, of 
course, are mainly suggestions. Further experiments are neces- 
sary before definite explanations can be made. 
SUMMARY AND CONCLUSIONS 
1. In Diemyctylus regeneration takes place readily after com- 
plete extirpation (exarticulation) whether the operation is made 
at the hip- or knee-joint (Part I), or at the ankle-joint (Part LI, 
Exp. 5). The time elapsed is somewhat longer than when a 
skeletal element is injured. 
2. The new skeletal elements are similar to the old. There is 
no tendency to reduction. 
3. The essential difference between regeneration after exarti- 
culation and regeneration after wounding a skeletal element lies 
in the behavior of the cartilaginous epiphysis which is present 
