l6 UNIVERSITY OF MISSOURI STUDIES [2O4 



which one chela was missing. The crayfish was kept in the labo- 

 ratory through the entire winter and spring. On June 9, 189?, 

 it died without having moulted since its capture. Up to this 

 time a new chela had not appeared, but as soon as the animal 

 died the cuticle stretched across the stump was dissected away 

 and immediately there burst forth a regenerated chela in which 

 at least four new segments had been formed (Figs. 9-10, PI. I.). 

 Fig. 9 shows the old basipodite together with the regenerated 

 portion immediately after the cutting away of the cuticle that 

 kept it so long from appearing. These parts are abnormal in 

 shape and proportion, owing to the very close quarters in which 

 they had been confined. Although the new growth was formed 

 entirely within the old stump, it was covered with a cuticle simi- 

 lar to the covering of a new appendage which appears in the 

 normal manner. In Fig. 10 the structure is seen from the oppo- 

 site side, after further dissection and after the specimen had 

 been in alcohol over night. That the new growth had been 

 formed for some time was evident from the color, if the 

 color of an appendage which develops normally can be taken as 

 a criterion, for, as was previously mentioned, after a new ap- 

 pendage is old enough to show all the new segments, it changes 

 from white to pink and finally to bright red. Fig. 1 1 shows a 

 longitudinal section of this rudimentary appendage. Compare 

 general outline with Fig. 10. Around the edges can be seen the 

 cuticle (cu), and just beneath this lie numerous nuclei (o) and 

 developing muscle fibres which radiate towards the central part 

 of the section. Throughout the limb there is a delicate network of 

 fibres beset with nuclei. The ground substance consists of a 

 non-cellular, granular material, the coagulated plasma (g). No 

 well-defined blood channels are present. At /> a well-marked 

 band of muscle fibres extends nearly across the segment. This 

 perhaps marks the constriction between two segments. At ^ a 

 constriction is present and a band of muscle fibres extends al- 

 most to the opposite side. There is very little reason to doubt 



