THE MEROTOMY OF CILIATED INFUSORIANS. 203 



B.— Merotomy of Stentor by fission.— When the Stentor 

 approaches the phase of fission, its nuclear chain shrinks up into 

 a rounded mass. The author shows, first, the part allotted to the 

 nucleus ; and then that each offset resulting fi:om the division of 

 the primitive individual acquires by means of the plasm its own 

 individuality before finally separating. He also finds that fission 

 does not take place if each of the offsets do not contain a nucleus 

 of its own. 



C— Merotomy of Stentor by Conjugation.— Stentors in conju- 

 gating unite together at the anterior extremities ; the nuclei of the 

 two individuals dissolve, and in their stead the micro-nuclei mul- 

 tiply by karyokinesis (or indirect division). On the separation of 

 the two individuals a new nucleus and nuclear chain appear in each. 

 The new nucleus '^ appears to be due to the blending of the micro- 

 nuclear substances of the two individuals. 



At the end of his paper Balbiani summarises his experiments 

 and his opinions as to their results as follows : — 



(i) The more or less large fragments which are separated from 

 the body of a Stentor generally close quite easily the wound pro- 

 duced by the section. This closing takes place almost immediately 

 owing to the contractility of the muscular fibres of myonemes (the 

 fibres of Lieberkiihn). When the w^ound is very large its closing is 

 often incomplete, and imbibition is then probably delayed, as in 

 the normal lacerations of the cuticle described by Schuberg, by 

 the superficial coagulation of the denuded plasm. 



(2) The local modifications of the wound and the contractions 

 of the body which aid in closing it must be considered as pheno- 

 mena of excitation determined by traumatism. This excitation 

 can be observed also in the movements of locomotion, where they 

 are manifested by a more rapid and less regular agitation of the 

 vibratile cilia, as well as by a greater frequency of diastrophy or 

 inversion of the normal direction of swimming. 



(3) The phenomena of excitation may be observed as well in 

 those merozoites containing nuclei as in those without any. After 



* In his previous researches (1861 — 62) Balbiani regarded the nucleus as 

 an ovarium and the nucleoli as a testis. (On the conjugation of the infusoria 

 and other relative questions, see Carpenter, " The Microscope and its Revela- 

 tions," 7th edition, by Dallinger, 1891, pp. 709 — 712.) 



