12 UNIVERSITY OF MISSOURI STUDIES [200 



not occur unless the animal is in its normal physiological condi- 

 tion, few of them are hardy enough to be kept all winter in con- 

 finement and still retain sufficient vitality to undergo a moult. 

 My most favorable results, especially in removing the entire eye, 

 have been obtained when crayfish were used soon after having 

 been brought into the laboratory during March and April. These 

 usually moulted within a few weeks and in some cases showed a 

 surprisingly rapid regeneration. 



III. OBSERVATIONS. 



In my observations and experiments especial attention has 

 been given to the regeneration of the chelipeds, antennae, tail- 

 fins, and the eyes, although experiments upon the ambulatory ap- 

 pendages, swimmerets, gills, and exoskeleton have been carried 

 on to some extent. The greatest part of my observations have 

 been confined to the eyes, but the discussion of the regeneration 

 of these organs will be reserved until the end. 



I. CHELIPEDS. 



It is well known that cra}^sh in common with other Deca- 

 pods practice autotomy, in case of the great chelae at least. The 

 break occurs normally between the basipodite and ischiopodite, 

 i. e., between the second and third segments. The cheliped at 

 this point is very much flattened and there is no movable joint 

 between basipodite and ischiopodite. Apparently a thin cuticular 

 partition is stretched across the appendage at this point and 

 when the limb is broken ofr this membrane closes the end of the 

 stump and prevents serious bleeding. A clot of blood soon 

 forms and in a short time the membrane turns brown and be- 

 comes more or less hardened. The length of time which expires 

 before the bud of a new limb appears depends upon a variety of 

 conditions, such as the time of year, the age of the crayfish, 

 whether or not the break occurs a short time after or a short 

 time before a moult, and upon other conditions both internal and 



