7 1 6 CALKINS. [Vol. XV. 



rying the tube from one staining pot to another. In all cases they were 

 cleared in xylol and mounted in balsam. For sectioning, either large quan- 

 tities of A'octiluca were imbedded in bulk, or individuals were selected and 

 imbedded separately. In most cases the latter method gave the most satis- 

 factory results, especially for dividing nuclei, where it was often desirable 

 to section in definite planes. Heidenhain's iron haematoxylin, the Biondi- 

 Ehrlich mixture, and Reinke's modification of the Flemming triple method 

 gave the best results in staining. Bordeaux red, orange, and eosin were 

 used as secondary stains with the iron haematoxylin. 



II. OBSERVATIONS. 



A. The Resting Nucleus. 



The nuclei of Noctihtca belong to the so-called vesiculate 

 type. They are spherical, oval, or elliptical in shape, and vary 

 considerably in size, the largest measuring about 5oAt in 

 diameter (Fig. 6), the smallest about 30/"', while those in the 

 various stages of spore-formation are still smaller. They are 

 always enclosed by a distinct, often thick, membrane, which, 

 although it disappears at certain regions during mitosis, is, as 

 a whole, retained through all phases of nuclear change. 



The interior of the nucleus consists mainly of two distinct 

 substances. One of these is granular and stains with acid dyes, 

 while it is so abundant that it gives a massive appearance to 

 the nucleus. The staining reactions of this substance show it 

 to be the same, probably, as the " oxychromatin " described by 

 Heidenhain ('94) in the nuclei of leucocytes. Unlike the latter, 

 however, the oxychromatin granules in Noctilnca appear to be 

 isolated bodies of large size and not suspended in a colorless 

 network, the "linin" of Heidenhain. The other substance 

 stains intensely green with the Biondi-Ehrlich mixture and 

 represents the "chromatin" of Flemming ('SO) or the "basi- 

 chromatin" of Heidenhain. In the resting nucleus the basichro- 

 matin is invariably collected in from eight to eleven, or more, 

 great chromatin reservoirs which, for the sake of brevity, may 

 be called the karyosomes in place of the earlier and more mis- 

 leading term, — nucleoli. By this use of the term, however, it 

 must not be understood that the karyosomes are local thicken- 

 ings of a general basichromatic reticulum. There is no such 



