No. 3.] ORGAA^S IN PHASCOLOSOMA GOULDII. 393 



ducts are the channels by which the secretion is conveyed to 

 the surface of the animal. The radiating threads surrounding 

 the sacks are probably to be regarded as continuations of the 

 reticulum of the cell. 



After the preceding part of this paper had been written and 

 the figures sent away to the lithographer, I had an opportunity to 

 obtain new material. In preserving this material, I took the 

 precaution to remove the cuticula from the tissue as soon as it 

 was placed in the fixing reagent, thus securing a very rapid 

 penetration of the fluid. The fixing reagents employed in- 

 cluded Hermann's and Flemming's fluids, corrosive sublimate, 

 and Graf's chrom-oxalic mixture. For staining, a number of 

 aniline dyes were employed, and the results obtained, besides 

 confirming the facts already presented, furnished some addi- 

 tional details regarding the cells in which the intracellular sacks 

 and canals are found. These new details have been presented 

 fully with figures in another place ^ and will be only briefly 

 reviewed here. Especially clear pictures were obtained from 

 material fixed in chrom-oxalic acid and stained with the Ehrlich- 

 Biondi triple mixture. With this stain, both when it is employed 

 upon material fixed in Hermann or upon that fixed in chrom- 

 oxalic, the wall of the intracellular sack is stained red, and is 

 seen to be surrounded by a second membrane, which also takes 

 the red color. Between the sack and this enveloping mem- 

 brane stretch the delicate radiating filaments which have 

 already been described as surrounding the sack. This mem- 

 brane surrounding the sack and limiting the filaments is always 

 present, even when the sack within has become so large as to 

 occupy almost the whole cell, and it is as well defined as the 

 sack wall itself. It is no mere boundary or limit of the proto- 

 plasm of the cell, as has been suggested in the first part of this 

 paper, but a sharply defined membrane distinguished by its 

 staining reaction from the cell protoplasm. The staining re- 

 action of the delicate radiating threads cannot be so positively 

 stated, for the exceeding fineness of these threads renders the 

 determination of their color a difficult matter. In some cases 



1 Zool. Jahrb., Bd. xiii, Heft i. 



