THE NUCLEUS 



83 



-s n. 



some when it is active in relation to the division of the nucleus, 



and a blepharoplast when it is in connection with flagella or other 



motile organs during the resting state of the nucleus. In this, 



probably the most primitive state of things, there are, further, two 



different structural conditions found to occur in different cases. 



First, the centrosome- blepharoplast maybe within, or closely 



attached to, the nucleus ; secondly, it may be quite independent 



of the nucleus, and some 



distance from it in the cell- 



body, during the resting 



state of the nucleus. In 



the first case of which an 



example is seen in Mastigina 



(Figs. 38, 39), paralleled by 



collar - cells in the Leuco- 



soleniid type of calcareous 



sponges the flagellum ap- 



pears to arise directly from 



the nucleus ; in the second 



case, exemplified by Mas- 



ligella (Fig. 40), and by 



collar-cells of the Clathrinid 



type, the flagellum takes 



origin quite independently 



of the resting nucleus. In 



both cases alike, the flagel- 



lum generally disappears 



before division of the nucleus 



begins; the blepharoplast 



becomes the centrosome, 



divides, and initiates the 



division of the nucleus ; the 



new flagella of the daughter- 



cells grow out from the two 



daughter - centrosomes dur- 



ing or after division of the 



nucleus, and in either case, 



when the two daughter-cells are completely formed, their centro- 



somes, as blepharoplasts, remain as the basal granules from which 



the flagella arise. 



2. The cell-body contains more than one body of centrosomic 

 nature namely, a definitive centrosome, in relation to the single 

 nucleus, and, in addition to this, one or more blepharoplasts in 

 relation to motile organs. Then, when division of the cell takes 

 place, one of two things may happen. 



Flo ^_ M astigdla vitrea, after 

 Goldschmidt (41). n, Nucleus, 



the cytoplasm. 



