6 BIOLOGICAL LECTURES. 



above. Incidentally, still another interesting question arises, 

 namely : Is it possible to identify any one of the three elements 

 in question — granules, continuous substance, ground-substance 

 — as the livijig substance or protoplasm proper, as distinguished 

 from a lifeless inetaplasm, and, if so, what are its structural 

 relations ? 



Could we positively answer all these questions, we should 

 have taken a long step forwards in the study of the cell. Far 

 from this, however, in point of fact hardly any two observers 

 have given exactly the same answers to them. Leaving aside 

 the earlier views, we find in the recent literature of the subject 

 two principal general views with a number of modifications of 

 each. 



The first of these agrees with the early view of Klein and 

 Van Beneden, that the protoplasm forms a network, 7'eticiilum, 

 or thread-work, composed of branching fibres embedded in a 

 homogeneous ground-substance which fills the interstices of 

 the network, and with granules or microsomes lying along the 

 course of the threads, or at the nodes of the network. Many 

 of those who adopt this interpretation further agree with their 

 predecessors, that the astral systems formed during cell-division 

 arise directly through a rearrangement of the preexisting net- 

 work about active centres of attractive or other forces, some- 

 what- as iron-filings arrange themselves along the radiating 

 lines of force in a magnetic field, — an arrangement which bears 

 a remarkably close though only superficial resemblance to the 

 protoplasmic amphiaster. Boveri, and some others, however, 

 regard the astral system as having no direct relation to the pre- 

 existing network, believing that the rays either arise from a 

 specific substance (" archoplasm "), distinct both from the gen- 

 eral network and from the ground-substance, or are wholly new 

 formations which, as it were, crystallize afresh out of the proto- 

 plasmic substance. 



The second view is that of Biitschli, who believes it to be 

 applicable to all forms of protoplasm, and who has been followed 

 by a considerable number of recent investigators. Biitschli's 

 interpretation differs entirely from the foregoing, the meshwork 

 being regarded not as a network, but as an appearance resulting 



