DIVISION OF COLLAR-CELLS OF CLATHEINA COEIACEA. 623 



stained by the osmic-picrocarmine method the nuclear 

 structure is not shown at all as a rule, but the nucleus simply 

 stains evenly pink. Sometimes the karyosome can just be 

 made out, sometimes not. A peculiar feature of the prepara- 

 tions is that the red. stain often does not extend up to the 

 nuclear membrane ; the stained portion forms a mass lying in 

 the centre of the nucleus, and between this stained mass and 

 the nuclear membrane a clear space remains, which can often 

 be seen to be traversed by delicate radiating lines, as if fine 

 filaments started from the membrane to support the central 

 stained mass. Comparison with nuclei stained with iron- 

 hsematoxylin shows in many of the latter a distinct alveolar 

 border to the linin-framework ; sometimes the alveolar 

 border is relatively very broad (fig. 36 e), and shows the 

 radiating partitions of the alveoli very distinctly. It would 

 appear as if the action of the osmic-picrocarmine method was 

 to cause a shrinkage within the alveolar border, with the 

 result that this inuer portion of the nuclear framework 

 contracts and appears as a homogeneous mass, which contains 

 all the chromatin and stains deeply, leaving the alveolar 

 border unstained. It should be noted that by no means all 

 the nuclei of the collar-cells show the clear border within the 

 membrane ; many of them stain evenly up to the membrane, 

 and this is always so in those cells which are about to 

 divide. 



The blepharoplast and flagellum stain black with iron- 

 hgematoxylin, but by the osmic-picrocarmine method they are 

 not stained. 



The cytoplasm of the collar-cells is finely granular and 

 usually very vacuolated. The neck is free from vacuoles as 

 a rule, but in many cases a round vacuole-like structure, 

 which differs in appearance from the other vacuoles, can be 

 seen in the neck region. The ordinary vacuoles in the body 

 of the cell are clear and appear as empty spaces, doubtless 

 representing drops of fluid in the living condition, but in the 

 direct line between the nucleus and blepharoplast there is 

 generally to be seen a vacuole, which has finely granular 



