26 SCIENCE PROGRESS. 



from simple geometrical considerations quite independently 

 of the ultimate form which will be finally assumed as 

 the result of specialised growth. And in applying the word 

 Non-cellular to those plants in which partition walls do not 

 occur, he merely gives formal expression to the fact that 

 these anatomical structures are absent, although in other 

 respects the plants in question conform with those usually 

 called multicellular, and they are not at all to be regarded as 

 consisting of a single enlarged cell. In fact he has expressly 

 stated that non-cellular plants are really the equivalent of 

 multicellular organisms in which the formation of internal 

 cell walls does not occur. More recently he has introduced 

 the term Energid (2) to express the physiological individu- 

 ality of those units I have here continued to call cells, and 

 he thereby emphasises the fact of their real existence 

 whether any positive anatomical boundaries can be dis- 

 cerned between them or not. 



It must however be clearly understood that in formulat- 

 ing the expression energid, Sachs lays especial stress on 

 the dynamical aspect of the relations existing between the 

 cytoplasm and the nucleus. But it will be admitted by most 

 people that a conception of force apart from the material 

 substance on or through which it acts, and by which its 

 operation becomes perceptible to the senses, belongs to the 

 domain of purely abstract ideas. We require to know far 

 more of the nature and structure of protoplasm before we 

 can usefully divorce our conceptions of force from our ex- 

 perience of matter in attempting to ascertain the nature 

 of those physiological causes of which all external form is 

 but the outward and visible sign. Sachs himself, however, 

 escapes the charge of vagueness, by restricting the applica- 

 tion of his expression so as to impose a territorial limit to 

 the sphere of influence mutually existing between each 

 nucleus and the surrounding cytoplasm. For him the word 

 Energid embodies the idea that the whole protoplasmic 

 region is partitioned into smaller provinces each dominated 

 by its own nucleus. And although it may be advantageous 

 for the seprovinces to be delimited from each other by cell 

 walls, permitting thereby a more complete independence to 



