120 Victor E. Emmel. 
and 7, the corresponding membrane of the chela of the lobster is 
composed only of connective tissue and does not appear to degenerate 
to any appreciable degree. On the contrary, in the lobster the origi- 
nal connective tissue membrane and the valves for the venous sinuses 
persist throughout the regenerative activities, and retain their original 
function in the new limb. In Fig. 7 it may be seen that as the 
regenerating epidermal cells begin to migrate across the stump they 
pass between the outer blood clot (bel), and the connective tissue 
membrane and the venous valves. ‘The venous valves no longer ex- 
erting a resistance to the blood stream, now begin to assume their 
original and normal position (Figs. 7 and 8). There is little, if 
any, degeneration of the connective tissue. In the blood clot, how- 
ever, the corpuscles soon deteriorate, the nuclei become flattened in 
the disto-proximal direction of the limb, and both the nuclei and the 
cytoplasm of the clot assume a deeper stain with hematoxylin and 
Congo red. 
9. Migration of Epidermal Cells.—As the blood clot forms, the 
epithelium of the exoskeleton retracts slightly within the stump. 
There is, however, no other noticeable change in the position of the 
epidermal cells until after the fourteenth hour following the opera- 
tion. The first regenerative activity which is then observed is a 
migration of ectodermal cells from all sides of the epidermal wall. 
This movement of the epidermal cells appears at first to be more 
pronounced in the region of the limb nerves on the inner side of the 
stump ; in a section taken through the outer side of the stump twenty- 
four hours after autotomy (Fig. 7) the migrating epidermal cells (e*, 
e!) from the opposite sides are still quite widely separated, but in a 
section from the inner side of the stump the migrating cells are found 
much nearer each other. These cells continue advancing centripetally 
until they unite to form a complete layer of epidermal cells over the 
surface of the stump. During the migration, the congested mass of 
blood corpuscles within the distal end of the stump begins to disinte- 
erate, but the old connective tissue remains intact as already de- 
scribed. 
3. Nuclear Changes in the Epidermal Cells.—The epidermal 
epithelium consists of low columnar or cuboidal cells, apparently 
