No. 3.] BIOLOGY OF THE STENTORS. 549 



form for this work. While my experiments have been much 

 less extensive and thorough-going than those of Gruber and 

 Balbiani, the results have confirmed theirs with reference to 

 the leading problem : viz., whether the presence of a portion 

 of the nucleus is essential for the regeneration of lost parts 

 and a continuance of the vital functions of a merozoon. Like 

 my predecessors, I have uniformly found that enucleate frag- 

 ments, even when of considerable size, soon perished without 

 regenerating any of the lost parts. Merozoa containing a 

 portion of the nucleus, on the contrary, were able to regenerate 

 the adoral zone, mouth, and contractile vacuole (Figs. 64 A and 

 64 B). Such merozoa invariably lost their blue pigment after 

 a day or two, and assumed a tawny color, such as often 

 appears in specimens of this species that are kept under 

 unfavorable conditions. I have never known the blue color to 

 be regained after it is once lost. 



Regeneration of the adoral zone takes place in a merozoon 

 in the same manner as in the normal Stentor, and is accom- 

 panied by the same meganuclear changes (Fig. 64 A and B). 

 Balbiani's figures ('92) show that an increase in the number of 

 nodes retained by the merozoon usually takes place at regenera- 

 tion of the adoral zone, just as in ordinary regeneration. But 

 I cannot agree with Balbiani's statement (p. 400) that the 

 increase in the number of nodes is accomplished by the con- 

 striction of pre-existing nodes, — a method which he evidently 

 believes to obtain in the normal condition of the Stentor ; for 

 he says (p. 400) : "Chez les individus normaux on n'observe 

 point une multiplication aussi active des articles du noyau, dont 

 le nombre augmente seulement de loin en loin par la division 

 d'un quelconque des articles preexistants. II faut en conclure 

 que, pendant la regeneration des merozoites, le fragment de 

 noyau qu'ils contiennent est le siege d'une excitation physio- 

 logique particulierement active, excitation qui se manifeste par 

 les regenerations organiques et la multiplication rapide de ses 

 propres elements." 



I have already expressed the opinion (p. 517) that the nodes 

 are increased only at time of renodulation ; and the "physio- 

 logical excitement" of which Balbiani speaks is nothing more 



