ON THE NUCLEOLI IN THE SOMATIC AND GERM 

 CELLS OF PEDICELLINA AMERICANA. 



LOUIS I. DUBLIN. 



In the course of a work on the germ cells of Pcdiccllina amcri- 

 cana, just published, (Dublin, '05), my attention was called among 

 other matters to the study of the character of the nucleolus, not only 

 in the various stages in the differentiation of the germ cells, but in 

 the somatic cells as well. Thus, in the resting condition of the cell, 

 the nucleoli are nearly everywhere in pairs and are situated at 

 opposite points near the nuclear membrane. This arrangement 

 is so constant, as are also the later processes through which these 

 bodies pass, that the possibility was immediately suggested that 

 Pediccllina might be one more instance among the many cited by 

 Hacker, '02, where there is a distinct outward expression of the 

 internal independence of the paternal and maternal elements, not 

 only in the nuclei of the early somatic cells, as is most clearly 

 observed in several forms, but also in the early germ-cells. It was 

 therefore determined to put this whole question to a test by an 

 examination of the cells throughout the whole life cycle, viz., to 

 observe whether the condition of the chromatin was actually in 

 accordance with the conditions so strongly suggested by the ap- 

 pearance and behavior of the nucleoli. 



For this purpose Pcdiccllina presents very favorable conditions. 

 In the first place, owing to the comparatively small size of the 

 polyps, the various tissues including the ovaries and testes, can 

 be brought into the same microscopic view, thus affording very 

 close comparison of these structures throughout. In the second 

 place, and more important, owing to the nature of the bud- 

 ding process and the internal development of the embryo, the 

 cells of all the stages of the life history are easily accessible for 

 study with the exception of a short and, for our purpose, rather 

 unimportant period during metamorphosis when the free swim- 

 ming larva leaves the brood-pouch and becomes attached. Such 

 a study of the entire life history is, finally, all the more important 



347 



