80 
Proceedings of the Royal Society of Edinburgh. [Sess. 
In 1898 (4) Morgan published the first of a series of papers on regenera- 
tion in the hermit crab (Eupagarus longicarpus). He first showed that 
power of regeneration is not related to liability to injury, and in a second 
paper demonstrated that, though regeneration takes place normally from a 
preformed breaking plane, nevertheless it can occur central and distal to 
this point. 
Steele (5) in 1904 published the results of work extending over several 
years. The observations were made on the regenerative process in the 
crayfish. A full description of the natural conditions influencing the rate 
and extent of reproduction of limbs is given, but the larger part of the 
paper is concerned with regeneration of optic peduncles, following on the 
work of Herbst. Cheliped regeneration is mentioned in the course of 
the work, but no details are given, and very little minute structure 
is described. 
In 1904 Reed (6) studied the regeneration of the first leg in crayfish, and 
pointed out that the new musculature for the limb is derived from the 
epidermis at the point of breakage. This demonstration of the fact that 
tissues of the same order can regenerate from different primary layers of 
the embryo brought the work into line with what had been seen in the 
regenerating head of Lumbriculus ; for here tissue derived from ectoderm 
in normal development regenerates from endoderm of the alimentary canal. 
The work of Reed differed from that which preceded, in that an attempt 
was made to discover the exact nature of the cellular change. Previous 
workers had confined themselves mainly to microscopic observations of the 
phenomena. Miss Reed, on the other hand, is concerned with minute 
structure, and on this account has probably failed to take note of 
several facts which are of great physiological importance. Observations 
on these points, when related to what is revealed by microscopic examina- 
tion, throw much light on such problems as the intimate nature of muscle 
contraction, or the functional relationship of the various parts of the 
contractile unit. For example, she does not mention the great changes 
which take place in the newly formed fibres on the occurrence of moulting, 
when the preformed limb increases in size fivefold almost immediately. 
Nor is any note made of the coming of function in the new muscle or the 
appearance of cross striations in the fibres. 
Emmel (7) in 1910 wrote an account of observations he had made on the 
regenerative processes in young lobsters. He described a valve mechanism 
for the stopping of haemorrhage at the breaking joint of the cheliped. 
One the same in principle but different in detail is present in the hermit 
crab, and the present writer studied it before he was aware of or had 
