304 LEONARD P. SAYLES. 



SUMMARY. 

 Nuclei and Nucleoli in Uninjured Individuals. 



1. The nuclei and nucleoli of the hypodermal cells are small 

 except in the growing tail region. Here they are enlarged, 

 especially in the cells on the ventral side which are involved in 

 the formation of the new nerve cord. 



2. Large nucleoli are present in the cells of the setigerous 

 glands near the growing region of the tail. In old segments 

 they are small. 



3. The gut nucleoli are small in the first twelve segments. 

 They are larger from this region up to twenty or thirty segments 

 from the posterior end. In these segments, they are again 

 small. 



4. Double nucleoli are occasionally found in the mid-gut, 

 where large nucleoli are present. 



Origin of New Tissue in Regeneration. 



5. Double nucleoli and mitoses are found in the intestine for 

 eleven or twelve segments from the wound. In this same region 

 the nucleoli are considerably enlarged. 



6. Cell proliferation in the old intestine practically ceases 

 between the sixth and seventh days of regeneration. 



7. Neoblasts metamorphose and migrate to the wound at the 

 anterior end as well as at the posterior end. At least eight or 

 nine segments furnish these cells, the four or five nearest the 

 wound apparently playing the most important part as observed 

 by Krecker. 



8. The failure of the muscle and nerve cells of the old part 

 to form the corresponding new structures in regeneration is 

 perhaps due to the fact that the cytoplasm of these cells has 

 become highly modified, thus rendering them less susceptible to 

 activation. 



9. The spindle-shaped cells in the dorsal portion of the bud 

 cavity at the anterior end are derived from the hypodermis and 

 not from the muscles of the old part. 



10. In both anterior and posterior regeneration the nuclei and 

 nucleoli increase in size in the ectoderm cells in the immediate 



