I02 ANDREWS. 



by which the endosarc of Vorticella is spHt apart to form a 

 new cleft, and represents a phenomenon common in proto- 

 plasmic masses, especially in pellicular membranes, in which 

 one frequently sees wave-like modulations. 



At different stages in their ever changing optical emphasis 

 and physical conditions, the aster rays show that difference 

 of reaction to chemicals which was spoken of under pellicles 

 as characteristic of the substance in its varying states of vis- 

 cidity or of contraction. A few seconds of time may make 

 a marked difference in reaction of these structures to harden- 

 ing fluids. It should also be marked that a false appearance 

 of viscidity, or of such physical states, can be produced by 

 too sudden changes in the density of reagents, or by osmotic 

 conditions caused by them. There is no doubt but that meth- 

 ods which do large justice to finer structural relations of the 

 protoplasmic elements, fail often to produce diagrammatic 

 karyokinetic figures, and it is therefore peculiarly unfortunate 

 that the presence of these structures should be made a test 

 of preservation, or methods. On the other hand, such appear- 

 ances are frequently had by less careful, more severe, or even 

 violent processes. Besides the results of my own special experi- 

 ments on this point, I have been struck with those gained by 

 others. In one case, during efforts to improve, by re-staining, 

 some unsatisfactory material, the investigator had plunged it 

 by mistake from ten per cent into ninety per cent alcohol, but 

 was rejoiced to find that it gained thereby fine karyokinetic 

 figures of the kind sought. The astral and nuclear structures 

 were strongly but coarsely marked and seemed destitute of 

 all finer protoplasmic relations while the cytoplasmic structure 

 of Biitschli was much vacuolated and altered. It seems that 

 vitiating changes may be wrought even after an initial harden- 

 ing and staining. Probably no amount of care and knowledge 

 of the conditions to be met can be too great for such experimen- 

 tal research, so delicate and susceptible are the protoplasmic 

 relations. And especially is this care needed where the irritable 

 substance is already in a state of organized contractility. 



Single fibrils in protoplasm, as well as contractile pellicles 

 and substance membranes were seen to become waved, or tor- 



