RELATION OF TRUE NUCLEOLUS TO LININ NETWORK. 12"J 



development, fate, and function of the nucleolus of Psdliodes, 

 and to compare these observations with those of a few other 

 workers who have incidentally noted facts along the same line. 



Origin. Since the chromatin and achromatin of the nucleolus 

 are indistinguishable in the early growth period, it is impossible to 

 follow the achromatic material back to its first appearance. 

 My observations, however, clearly show that its origin is in 

 some way related to the chromatin. This suggestion does not 

 corroborate the views of Montgomery and many earlier workers, 

 but finds support in the observations of a large number of later 

 investigators. The theory of the extra nuclear origin of the 

 achromatic nucleolus, as set forth by Korschelt ('89) and strongly 

 supported by Montgomery ('98) readily loses its significance, at 

 least in general application, when the life history of the nucleolus 

 of Pselliodes and similar forms are understood. The only proof 

 set forth in support of this view is the fact that such nucleoli 

 first appear in contact with the nuclear membrane. In many 

 forms, the true nucleolus not only originates independent of, 

 but completes its life history without being in any way associated 

 with the nuclear membrane. Medes ('04), for example, notes 

 that in the growth period of Scutigera forceps the chromatin 

 accumulates, forming a karyosphere which seems to be of an 

 achromatic nature, although containing the chromatin in granular 

 form. The granules finally emerge leaving an achromatic mass, 

 containing an accessory chromosome. The achromatic material 

 now breaks into small rounded bodies, which soon become in- 

 distinguishable. The true nucleolus of Philosamia cyntliia (De- 

 derer, '07) also appears in a mass of chromatin entangled in 

 the spireme threads of the last spermatogonial stage. In this 

 and later stages, it is characteristically bipartite, one end of 

 which usually stains darker, no doubt from the fact that it con- 

 tains more chromatin granules. In its typical form, the idio- 

 chromosomes are attached around the middle of the double 

 achromatic nucleolus in the form of a deep crescent-shaped band. 

 This band later becomes shorter and broader until it loses contact 

 with the nucleolus, which then disappears. 



Although these citations will suffice to show that in many 

 forms there is a certain uniformity in the early history of the 



