THE CrELOMIO FLUID IN ACANTHODRILIDS. 579 



in absolutely fresh cells, but when the cell is examined in 

 salt solutions or even after exposure to air^ soon becomes 

 marked, and is still more intensified by the use of reagents. 

 The inclusion seems, then, to be a semi-solid spheroidal 

 structure, which is easily disintegrated into a " thread." 



Turning now to the less frequent condition where a multi- 

 plicity of "rings" exists (as observed in certain immature 

 specimens examined in July). The earlier phases are iden- 

 tical with the one first described, but in place of a single, 

 large, central vacuole two, or more, smaller and irregularly 

 distributed vacuoles make their appearance (fig. 16) ; each of 

 which, then, becomes surrounded by a refringent ring, which 

 usually remains simple (fig. 17, etc.). 



Action of Reagents. — Stains. — Gentian violet stains the 

 thread and the fluid in the vacuole very rapidly a bright 

 blue ; it is the first of the cells of the fluid to take the stain ; 

 the nucleus is stained violet. 



Iodine stains the thread a bright yellow, much more deeply 

 than the cytoplasm. 



Acids, Alkalies, etc. — Nitric acid. — At the fii-st contact 

 the cell membrane shrinks somewhat, and the thread becomes 

 more evident. But soon the cytoplasmic envelope becomes 

 coagulated, the transparency being replaced by opaque granu- 

 lations that conceal the thread within. The cell swells, and 

 these granules then give place to a series of radial lines (fig. 

 23) ; while the thread is concealed, and in the first experiments 

 I believed that it had beeu reduced to granules which are 

 more refringent than those of the cytoplasm; finally, the 

 cell membrane becomes ruptured, and the thread issues in 

 loops from the margin (fig. 24), sometimes at one point only, 

 though usually at several points round the circumference. 

 The radial lines observed in the cytoplasmic envelopes are 

 probably caused by the " unravelment" of the thread, and 

 represent the limbs of the loops that ultimately burst out of 

 the cell. 



Boiling nitric acid reduces the whole thread to granules, 

 which are not dissolved by further action. 



