ORGANIC FORM AND ARCHITECTURE -70s 



cell and of its nuclear cliromosomes in particular. The microcosm 

 of a typical cell includes the following structures: 



(a) There is the general cell-substance or cjrtoplasm, consisting 

 partly of the genuinely living protopla^ and partly of materiali 

 (metaplasm) not really living. 



(b) Almost invariably there is a kernel or nucleus, also proto- 

 plasmic and also a little world in itself. 



(c) A specialised body, called the central corpuscle or centrosome, 

 lies in the cytoplasm near the nucleus. It divides into two before 

 cell-division occurs, and seems to play an important part in the 

 process. 



(d) In the cytoplasm there may be formed bodies more or less 

 permanent, which are quite different from temporary stores of 



2. 



Fig. 105. 



Two Living Chromosomes showing their paired state and irregular outline. 



After McClung. 



reserve material and the Hke. Thus there are often scattered 

 "mitochondria", thread-Uke or rod-hke in appearance, which have a 

 role in the characteristic activity of the ceU, e.g. whether nervous 

 or glandular. They are often visible in living cells. Then there is 

 the knot-like "Golgi apparatus", probably part of the genuine 

 protoplasm, and very generally present though difficult to demon- 

 strate. Third, there are "chromidia", consisting of immigrant frag- 

 ments or extensions of the nucleus. 



(e) Enclosing the whole is a semi-permeable cell-membrane, 

 usually very deUcate in animals, strengthened in plants into a very 

 definite cell-wall of cellulose. 



The Nucleus.— The centre of the ceU, the nucleus, was discovered 

 more than a century ago by Robert Brown. It is a much studied 

 world, and the details presented by fixed and stained specimens 

 seem to correspond somewhat closely to reality. In a normal 

 resting nucleus there is a fine skein of a material called "linin". and 



