NUCLEI OF MUSOLB-FIBEE IN NECTURUS LATERALIS. 463 



furrows occupy one part of the surface of the membrane, the 

 remainder of which is possessed of a series running in a contrary 

 direction. They may be arranged parallel to the length of 

 the fibre, or, as in 8, perpendicular to the long axis of the 

 nucleus, or, as in 7 and 9, oblique to the same. Often one 

 finds a combination of the two last mentioned modes of 

 arrangement as represented in 10. Cases were observed in 

 which a furrow, followed a part of the way around the nucleus, 

 was found to divide at an acute angle, the branches completing 

 the rest of the nuclear circumference. If the nucleus is flattened 

 it is usual for the furrows to be confined to one surface. In 

 7 and 9 the number of these is respectively three and two, 

 and in 8 they are very numerous. The depths of the furrows 

 vary with their breadth, the latter being estimated by the 

 breadth of the violet line of reduced gold. The depth in some 

 nuclei is such that when one takes an optical section of them 

 the nuclear cavity is almost divided into a series of separate 

 compartments (25). The distance of the furrows from each 

 other is subject also to considerable variation (10, 12, 15). 



The cause of these furrows is in all probability the pressure 

 exercised by the trabeculse of the muscular reticulum described 

 by Melland,^ the transverse trabeculee giving rise to the trans- 

 verse furrows, the longitudinal ones to the furrows running 

 parallel to the long axis of the nucleus. 



Here in passing I may refer to my own observations on this 

 muscular reticulum. These were made on specimens obtained 

 with gold chloride from the rabbit, frog, Necturus, crayfish, 

 and grasshopper, and as a result I accept in full the views of 

 Melland. In my preparations of the muscle-fibre obtained 

 from the rabbit and Necturus this reticulum is in all its 

 aspects splendidly demonstrated. Carnoy^ apparently holds the 

 same view as to the cause of the striation of the muscle-fibre 

 in Hydrophilus piceus, for he describes it as due to a re- 

 arrangement of the reticulum of the cell (cytoplasma of that 



1 " A Simplified View of the Histology of the Striped Muscle-fibre," this 

 Journal, July, 1885, p. 371. 



2 ' La Biologic Cellulaire,' Paris, 1884, pp. 192 and 193, fig. 38, 



