THE NUCLEUS 



83 



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 may be 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- 

 tigella (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 \ FK , Q. Mastigdla i-itn-n, after 

 before division of the nucleus \ Goldschmidt (41). n, Nucleus, 

 -U Q fi, r KlArJiflT-rml'Kjf \ almost obscured by the mass of 

 begins , blepnaroplas \ food -bodies of various kinds in 

 becomes the centrosome, j t h e cytoplasm, 

 divides, and initiates the 

 division of the nucleus ; the 

 new flagella of the daughter- 

 cells grow out from the two 

 daughter - centrosomes dur- 

 incr or after division of the 



O 



nucleus, and in either case, 



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

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

 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 eel! 

 place, one of two things may happen. 



