98 



BIOLOGY: GENERAL AND MEDICAL 



shape. Rarely in the cells of certain arthropods the 

 nuclei may be branched or even reticular. Diseased 

 cells may also show breaking up or fragmentation of the 

 nucleus karyorhexis or solution of the nuclear mate- 

 rials karyolysis. 



The cell wall that formed so essential a part of the 

 primitive conception of the cell is an extremely variable 

 structure. The lowest forms of life are commonly with- 



Pio. 30. Cells with variously shaped nuclei, a, Vorticella, a ciliated 

 infusorian with a sausage-shaped nucleus, b, Stentor, a ciliated infusorian 

 with a rosary-like nucleus, c, Cells from the silk glands of a caterpillar, with 

 nuclei branched like stag's antlers. (After KorscheU.) 



out it, and the greater number of the cells of the metazoa 

 are without it. 



In its most primitive form one sees nothing but a 

 transparent hyaline border to an elsewhere granular cy- 

 toplasm. Under these conditions it is sometimes spoken 

 of as the ectosarc, to differentiate it from the endosarc 

 or cell substance. As the evolution of the structure is 

 followed, it is found that it modifies certain of the phys- 

 iological manifestations of the cell. Thus, the amceba 



