No. I .] POL VCHOERUS CA UDA TUS. S I 



In the ova of Allolobopliora foctida Miss Foot found that 

 the blue stain attacked the archoplasm and the spindle fibers, 

 while in the ova of P. caiidatiis its greatest afifinity seems 

 to be to the lifeless dotter material, both while in the vitella- 

 rium and later while in the ova. It is curious that these stains 

 should act so differently on the ova of different animals. It 

 is unfortunate that this lithio-carmine and Lyons blue are 

 most valuable when the material has been killed in corrosive 

 sublimate, and are almost worthless where Hermann or any osmic 

 acid reagents have been used. Sublimate is the killing reagent 

 employed by Miss Foot, and from ova so treated she obtained 

 the beautiful figures shown in her paper. As narrated above, 

 sublimate shrinks and distorts the spindles in Polychocrus ova to 

 such an extent that it has much less value as a reagent. Many 

 animals killed in this way to study the vitelline glands proved 

 to contain ova in which the first segmentation spindles were 

 formed. The spindle fibers were often bent or distorted look- 

 ing, but the general outline of the spindle was distinctly red and 

 the periphery of the ovum equally distinctly blue. In no case 

 have I found any substance taking the blue stain in the ovum 

 which appeared to be archoplasmic or nucleolar in its origin. 



In every individual, whether killed before, during, or after 

 the breeding season, immature ova closely clustered near the 

 lateral margins, quite close to the ventral wall of the body, are 

 conspicuous in sections. The ovarian ova (Fig. 5) are, as a 

 rule, oval in form, but are often packed so closely together 

 that almost any outline is possible. The dividing cell walls 

 are exceedingly indistinct and only to be made out in very 

 well-stained sections. The ova are finely granular, and show so 

 much greater afifinity for almost all stains than do other tissues, 

 that, in sections in which the ovarian ova are the special object 

 of study, the color must be drawn until the other tissues are 

 but slightly tinged. 



Even the nuclei of mature ova stain less vividly than do those 

 of immature cells. The probable reason for this is that at this 

 stage the whole protoplasm which is to constitute a part of the 

 future ovum is concentrated within the unripe ovum, and is 

 undiluted by the food yolk, which stains less intensely, and 



