91 
1914-15.] Regeneration of the Legs of Decapods. 
contraction. The presence of abundant sarcoplasm is also lacking in the 
new fibres. It is hoped that by microchemical and other methods some 
light may be thrown on this phenomenon and on the very much broader 
problem of the intimate nature of muscle-contraction. 
Summary. 
(1) Homarus vulgaris, Engyagurns hernhardus, and Carcinus moenas 
all form limb-buds or papillse in the process of limb regeneration. These 
are covered by a chitinous envelope, and the observations here recorded 
show that their outer form and size are adaptations to the requirements of 
the animal. That of the lobster is straight, that of the hermit crab curved, 
while the shore crab has a papilla which may be folded on itself three 
times inside the envelope. 
(2) Valvular action of the diaphragm at the breaking plane plays a 
greater part in the stopping of haemorrhage after self-amputation than 
clotting, and the dilatation of small vessels which pass beneath the 
epidermis detaches a layer of cells. This layer of epidermis proliferates 
from its free edges to form the new limb. 
(3) A new diaphragm is the first structure laid down, and differentiation 
takes place from the base outwards. Muscle arises at the growing tip from 
cells proliferated from the old epidermis (an ectodermal structure), and the 
nerve grows outwards from the torn end by cell proliferation. 
(4) Muscle-fibres are anatomically complete immediately before moult- 
ing. The fibrillse are cross-striated and enclosed in a sarcolemrna, but full 
functional activity does not come till several days after moulting, beginning 
with slow rhythmic movements. Sarcoplasm seems to be less plentiful 
than in the normal fibre. 
(5) When moulting occurs the papilla is at once expanded to several 
times its previous size by valvular action, and the epidermis, previously 
composed of several layers of cells, now thins to a single layer, as is seen in 
the normal limb. 
The expenses of this research were defrayed by a grant from the 
Carnegie Trust. 
