Physiology and Biology of the Protozoa, 475 



Stentor cteruhus is particularly well suited for the observation 

 of the mode in which injuries to the external surface heal up 

 again, on account of the broad blue stripes of the cortical layer. 

 Thus if we- make a short sharp cut in the cortical layer with 

 the scalpel, the animal of course shrinks together and the 

 wound at once closes, but at the same time the stripes 

 and the muscular fibres are still separated by the cut at the 

 place affected and can only gradually grow together again. 

 In a few hours, however, this is also effected, but usually so 

 that a displacement has taken place, the corresponding ends 

 not having found each other, and furcations and bendings of 

 the stripes are produced which always betray the place of 

 the incision. The mobility of the Infusorian is, however, 

 by no means affected by this, and indeed, even in the normal 

 animal, furcations of the stripes and muscular fibres very often 

 occur towards the anterior extremity. The mode in which 

 the extremities of the cut muscular fibres endeavour to find 

 each other and finally grow together again no doubt resembles 

 on a small scale the course of events which we have to imagine 

 in the process of wound-healing in the muscles of higher 

 animals. 



As regards the complete division of the Stentors into two 

 or more parts, I have already remarked that this usually leads 

 to the production of the same number of perfect Infusorians 

 as there were pieces, although with a limitation, as will be 

 shown hereafter. With some practice the section itself is 

 easily performed, if a tolerably sharp little scalpel is employed, 

 only it is often difficult to ascertain the right quantity *of 

 water ; for if the drop on the slide is too large the Infusorian 

 swims away from under the knife, while if it is too small the 

 Stentor becomes too much flattened out and quickly deli- 

 quesces after the section is made. I may here mention, how- 

 ever, that the deliquescence may be prevented by quickly 

 adding water, and that Stentors which have already suffered 

 considerable loss of substance may recover and become per- 

 fectly regenerated. 



If the section has been cleanly made and the quantity of water 

 rightly adjusted, the two wounded surfaces immediately close 

 again, and the two halves swim briskly about ; they may be 

 fished out with the pipette and isolated, which is best done in 

 small watch-glasses, and then in the course of from twelve to 

 twenty-four hours the lost parts are completely replaced in 

 each of the pieces. If we employ a lens or a low power of 

 the microscope the sections may be carried in any pre- 

 determined direction ; and it then appears that the regeneration 

 occurs most rapidly and completely when the section has gone 



