284 E. A. MINCHIN. 



The nuclei are very large, each surrounded by a clear space. 

 In sections this space appears filled by a finely granular or 

 streaky coagulum (fig. 7). It sometimes appears as if the 

 nucleus were suspended in this place by threads (fig. 6), but I 

 think this appearance is only due to coagulation of the fluid, 

 probably albuminous, which filled these spaces during life. 

 The nucleus itself is about 50 ju in diameter, and surrounded by 

 a strong nuclear membrane, which usually appears wavy in 

 section, owing, doubtless, to shrinkage. It has a single large 

 nucleolus about 25 /x in diameter, the remaining space of the 

 nucleus being filled with cloudy or very finely granular con- 

 tents, with a number of darker spots. At first it seemed as if 

 these dark spots might represent the nodes of a fine reticulum 

 supporting the nucleus, but I was unable to detect any such 

 reticulum with the Homogen. Immers. 2*0 mm. of Zeiss 

 (fig. 8 a), and the nucleus appeared to be filled with a fine 

 coagulum, but of a different nature from that filling the clear 

 space surrounding it. It is possible, or even probable, that 

 the nucleolus is kept in place by fine strands of chromatin or 

 other substance fastening it to the nuclear membrane, without, 

 however, any definite reticulum. 



The nucleolus itself deserves particular description on 

 account of its peculiar structure. In the sections through A 

 it appeared as a round spot, very darkly stained (with hseraa- 

 toxylin), containing a lighter vacuole-like spot somewhat ex- 

 centrically placed. Examination of the thin sections through 

 B made clear the real structure of the nucleolus (figs. 8, 8 a). 

 It consists of a darkly stained ground substance containing an 

 immense number of clear vacuoles of all sizes. One of the 

 vacuoles is much larger than the others, and being excentrically 

 placed, constitutes the clear spot seen in the thick sections. 

 Some are excessively minute, and almost escape detection. In 

 fig. 8 a the minute vacuoles can be seen in the obliquely cut 

 wall of the large vacuole, producing an appearance which under 

 lower magnification looks like a network. 



The darkly staining ground substance of the nucleolus 

 should, after the analogy with the cell nuclei of higher animals, 



