Physiology and Biology of the Protozoa. 479 



Another experiment is as follows : — A Stentor was, on the 

 28th April, divided transversely into two halves, both of 

 which had become regenerated on the following day ; on the 

 30th the two artificially produced daughter-individuals had, 

 almost simultaneously, divided again spontaneously. In two 

 other artificially separated divisions also^ one of which had 

 been at first deformed, natural fission occurred simultaneously, 

 as also in a third experiment. We thus learn from observa- 

 tion the interesting fact that tivo artijicially produced halves 

 are able to increase ^spontaneously at exactly the same time^ 

 although after section they were apparently not equivalent, 

 and the anterior portion, which still possessed the most com- 

 plicated part of the body, the peristomial area with the mouth 

 and oesophagus, really had only to go through the process of 

 wound-healing, while the posterior portion must have pro- 

 duced all the above organs anew. Nevertheless it was able 

 to answer to the impulse leading to fission just as quickly as 

 the other. This also is a proof that the material for new-for- 

 mations in the Infusoria is not stored up predisposed as such, 

 but that the elementary parts above indicated as primitive in 

 the protoplasm are convertible at any time. That the impulse 

 to fission, which, as will be shown hereafter, we must seek in 

 the nucleus, occurred simultaneously in the two separated 

 portions cannot surprise us if we consider that the nuclear 

 constituents present in them were in connexion only a little 

 while before, and therefore must have agreed in their consti- 

 tution and in their action upon the protoplasm. 



I may mention, in conclusion, that regeneration caru be 

 produced also in parts which are not completely separated from 

 each other, so as to form Stentors with two anterior or two 

 posterior ends. Thus, for example, I had divided a Stentor 

 by a longitudinal incision m such a way that one of the two 

 halves, which were still connected behind, retained nearly the 

 whole peristome and the other only a small part of it (fig. 5) ; 

 tlie former immediately completed itself again, but in the case 

 of the second half some days elapsed before it had again 

 developed a perfect peristome with the mouth (fig. 6). Thus 

 two perfect Stentors, only united at the base, were produced, 

 and they further contained a connected chain of nuclear joints. 

 Unfortunately 1 could not keep this pair of twins long alive, 

 as the water in which I had isolated them became foul. In the 

 same way we may succeed by means of incomplete longitu- 

 dinal sections in producing animals which show two posterior 

 ends attached to a common fore part. However, halves 

 divided in this way do not always remain connected, but 

 usually they tear themselves apart by twisting movements. 



