Energies of the Organic World 83 



in increasing number and in more and more intimate connection 

 T\'ith each other that give definitely recognizable chemical and 

 staining reactions in common. These further react like the 

 refractive chromatin substance of the nucleus and nucleolus of 

 caryotic cells. In some species or genera they are few in num- 

 ber, small in size, and comparatively scattered; in others they 

 are fairly large, aggregate, and uniform; or again they are 

 united by delicate chromatin threads so as to form a central 

 connected skein or network of granules of loose open pattern. 



Between such arrangements and the fully formed nuclear 

 structure of all caryotic cells, there seem to be the most per- 

 fectly graded examples and phases. So from nucleo-protein 

 granules to granule loops, from these to an open network, from 

 this to a closed network with bounding chromatin membrane, 

 and finally to a nuclear network or basket that encloses and 

 hangs a special nucleo-protein mass or nucleolus, the transitions 

 are still left to us and can be followed stage by stage.* 



As to the molecular and chemical constitution of the sub- 

 stance chromatin, most biochemists and physiologists are 

 agreed that it is a highly complex protein compound, which is 

 excelled only in organized complexity by Nissl's granules (which 

 wdll importantly concern us later) of animal nerve cells. Unlike 

 the simpler proteids of protoplasm, it is devoid of sulphur, but 

 is rich in phosphorus. By compounds of the latter it holds 

 iron in its substance, either as an integral constituent or more 

 probably to promote conductivity of energy currents. As ex- 

 plained later we consider that it exists in most concentrated 

 state in the nucleolus, whence it extends outward as a sponge 

 network whose threads are intimately fused as a nuclear net- 

 work, in the interstices of which is protoplasmic or nucleo- 

 plasmic substance, and again processes of it — the kinoplasmic 

 threads of some cytologists — extend into and throughout the 

 general cell protoplasm as a fine network. 



* The above conclusions, as well as those set forth in an already quoted 

 article {13: 252) by the writer, have been confirmed in a recent valuable paper 

 by Miss Acton (Ann. of Bot. 28 (1914) 433), who has given detailed attention 

 to several of the unicellular Cyanophyceae. 



