RELATION OF TRUE NUCLEOLUS TO LININ NETWORK. 123 



maturation prior to the synaptic stage correspond in general to 

 those of Oncopeltus as given by Wilson ('12). It was further 

 noted, in agreement with the observations of Payne ('12), that 

 the oogonial number of chromosomes is thirty, the spermato- 

 gonial twenty-eight, and the first spermatocyte sixteen. The 

 metaphase plate of the second maturation division shows twelve 

 chromosomes arranged in a more or less uniform circle surround- 

 ing four (three small and one large) sex-chromosomes. 



A. ORIGIN, DEVELOPMENT AND FATE OF THE NUCLEOLUS. 



The contraction stage presented in Fig. i is of considerable 

 duration. As this figure shows, the chromatin threads are thick 

 and stain intensely. The threads even though in a contracted 

 condition, exhibit a certain degree of polarization, many of the 

 fibers terminating in the vicinity of the nucleolus, but seldom 

 if ever coming in contact with it. 



Embedded in the periphery of this mass of chromatin threads 

 lies the large, compact, well-defined nucleolus surrounded by a 

 vacuole-like space as described and illustrated by Wilson ('12) 

 in Largus and other forms. As he says of Largus (Figs. 78 to 80), 

 "no definite wall to the vacuole can be seen, but the chromatin 

 threads are often seen encircling its outer limit as if lying upon 

 a definite substratum." This noteworthy feature is character- 

 istic of all the preceding stages back to the telophase of the last 

 spermatogonial division. However, in the earlier stages the 

 body is somewhat smaller and more spherical in form. This 

 slight increase in size and the change of shape suggests a certain 

 degree of activity prior to the stage represented in Fig. i . After 

 this period, however, the growth is so rapid that seldom can 

 two adjacent cysts be found which show the same stage of 

 nucleolar development. 



Under ordinary staining conditions the nucleolus shows no 

 differentiation in the structure until after the nuclear wall has 

 formed (Fig. 15). In fact the condition was so universal that 

 up to this stage the nucleolar body was first considered solely 

 chromatic in nature. Later observations, however, revealed the 

 fact that the nucleolus is not a homogeneous body but composed of 

 both chromatic and achromatic material. This conclusion is based 



