466 A. B. MAOALLUM. 



tracts with the muscle-fibre and extends with it again, yet not 

 passively. 



The possession of an irregularly meshed reticulum by the 

 nucleus would imply on the part of the latter movements, if any 

 at all, of an amoeboid character. It is possible that this is just 

 what occurred in the nuclei represented in fig. a, 10, 12, and 17, 

 an unequal extension or contraction of all parts of the nucleus, 

 resulting in a misplacement of the furrows and in their irregu- 

 larity. 



Nicolaides suggests that all muscle nuclei take a more than 

 passive share in muscular contraction. 



Some nuclei have part of their surface completely free from 

 furrows (fig. a, 5). I think this is due to the fact that the whole 

 of the nuclear body is not surrounded by the muscle- substance, 

 a part of it lying between the latter and the sarcolemma. 



EXPLANATION OF PLATE XXXIII, figs. A and B. 



Illustrating Mr. Macallum's Paper on the " Nuclei of the 

 Muscle-fibre in Necturus lateralis.^' 



Fig. A, 1 — 25. — Nuclei of striated muscle-fibre of Necturus lateralis, 

 11, 20, 21, 22, representing some from the heart muscle. Mode of preparation : 

 gold chloride, formic acid. 



Fig. b. — A part of a striated muscle-fibre with its nuclei, from Necturus. 

 Gold chloride, formic acid. 



(Note. — In drawing these figures, Leitz obj. 7, and oc. 1 or 3 were 

 employed.) 



