No. 3-] MORPHOLOGY OF THE STENTORS. 533 



organs is the more striking, inasmuch as there seems to be no 

 occasion for the regeneration of more than one of the zones. 

 At the stage represented by Figs. 61 A, B, it is the mouth on the 

 left {i.e. posterior) that is wanting, while in the later stage (Fig. 

 61 D) the mouth on the right is absent. The only explanation 

 of this synchronism in the development of duplicate parts 

 seems to be a close coordination of functions throughout the 

 dual organism, which therefore physiologically is to be regarded 

 as a single individual, but with duplicate organs and functions. 



The double Stentor underwent little modification during the 

 next nine hours, in the course of which it was .frequently 

 examined. The new mouths (o.,-^ o.^) were gradually drawn into 

 position, and o.- atrophied. By the following morning, 25 hours 

 after Fig. 61 D was drawn, a great change had taken place (Fig. 

 61 E), amounting to a loss of dualism, and therefore a return 

 almost to the normal condition. The right-hand mouth {0. •*) 

 had atrophied. The breaks in the zone had, with one exception, 

 disappeared ; the frontal field was much reduced in size, and 

 its two systems of stripes had nearly melted into one. Only 

 one contractile vacuole (c.v.'^) was present. The regeneration 

 (a.s.^) of the oral apparatus (0.'^) was in progress, but no similar 

 regeneration was under way for the atrophied o.^ — strong 

 evidence of the loss of physiological duality. 



The subsequent modifications of our Stentor were unim- 

 portant, and consisted mainly in the obliteration of every trace 

 of duality. After a day or two it differed from normal Stentors 

 only in the slightly greater size and oval shape of the frontal 

 field. No fission occurred during the four or five days I had 

 the Stentor under observation. 



One of the double monsters studied in detail by Balbiani 

 ('9l) differed from mine in that duality was present, not in the 

 anterior, but in the posterior portion of the body. The monster 

 was furthermore artificially produced by amputating the frontal 

 field and dividing the posterior part of the body by a longi- 

 tudinal incision, so as to give it a bipedal appearance. The 

 regeneration of the frontal field was not observed. The 

 interesting point of likeness between Balbiani's specimen and 

 mine is the gradual obliteration of duality and return to the 



