462 A. B. MAOALLUM. 



Necturus macerates and disintegrates very easily in solutions 

 of formic acid. 



The long diameter of the nuclei, the largest and the smallest, 

 measures 0*037 — 0"053 mm., and the transverse diameter 0"010 

 — 0*025 mm. The form of the nucleus varies somewhat, the oval 

 being the most common ; oblong and quadrate ones were occa- 

 sionally observed. The membranes of old nuclei have apparently 

 the capacity for attracting the reduced gold. In what might 

 be considered as young nuclei, the membrane is not furrowed 

 or but slightly so, and the chromatine is usually quite distinct, 

 arranged in short, variously looped pieces along the long axis of 

 the nucleus, or in the form of minute nodules (nucleoli) in 

 different positions in the nuclear cavity (fig. a, 1 and 24). The 

 reticulum of achromatine, or, better, caryoplasraa, with the 

 meaning attributed to that term by Carnoy, is very delicate 

 with very narrow meshes in the nuclei just referred to. A very 

 large number of the nuclei observed lacked chromatine while 

 their caryoplasma was more prominent and its meshes larger. 

 In a few, a further modification of the reticulum, to be described 

 belonr, was observed. 



In view of Nicolaides'^ work on the division of nuclei in the 

 frog's muscle, I made a careful search for like cases of division 

 in Necturus, but the result was disappointing. Out of many 

 hundred nuclei which I examined I found but one case of 

 division, and that from the heart-muscle (fig. a, 11). Flemming^ 

 observed indirect division of the muscle nuclei in larval but not 

 in adult Amphibia. My failure to find in Necturus what was 

 observed by Nicolaides in the frog could not have been due to 

 the reagent, gold chloride, for I found negative results when a 

 mixture of chromic and acetic acids, or of these and osmic acid, 

 was employed. 



Nine out of ten of the old nuclei, i. e. those in which there 

 remains no trace of chromatine, have markings and furrowings 

 on their surface. Sometimes, as in fig. a, 2, a series of parallel 



' " Ueber die Karyokinetische Erscheinungen der Muskelkorper," * Arch, 

 fiir Auat. uud Pliys., Phys. Abth., 1883, p. Ul. 

 2 ' Zellsubstauz Kern- uiid Zelltheilung,' Leipzig, 1882, p. 337. 



