IOWA ACADEMY OF SCIENCES. 
169 
injury than are the left. While it can not be stated defi- 
nitely that this is so, it may be that there is a tendency 
for crayfishes to be “right-handed” — to use their right 
appendages, especially the chelipeds, more than the left; 
these are used either offensively, defensively, or in procur- 
ing food, and are thus much exposed to the attacks of 
enemies or accidental injuries. 
The antennae and chelipeds, in most cases, were broken 
or missing from the “breaking-joint”. This was not true 
with regard to the walking legs as no such joint is dis- 
tinguished in them; they were missing at various points as 
indicated by the abbreviations given on the chart. 
The almost entire lack of injury to any of the abdominal 
appendages seems to be due to their small size, their func- 
tion, and the protection afforded them by that portion of 
the body as contrasted to the more exposed, larger and 
more functional thoracic appendages. 
At first sight there seems to be a definite relation between 
the liability of the appendages of the crayfish to injury 
and their power of regeneration. The appendages more 
exposed to injury, accidental or otherwise, are the ones in 
which regeneration is best shown, w T hile those rarely or 
never injured show apparently but little power of regener- 
ation. But, if we study the process of regeneration more 
closely, we find this relation to be apparent only, as regen- 
eration takes place in the walking legs of all crustaceans, 
while the chelipeds alone possess a “breaking-joint”. If 
the walking legs are injured regeneration takes place at 
any point and there is no definite relation between the 
liability of a part to injury and its power of regeneration. 
The above notes are merely preliminary in character 
and will be followed later by further results bearing upon 
other phases of regeneration. A large number of individ- 
uals both male and female collected at various seasons will 
undoubtedly throw much added light upon the subject of 
regeneration under conditions of normal environment. 
