154 Harry Lewis Wieman. 



less of the killing agent employed, the food stream does not show 

 the same constancy in behaviour. After Flemming's solution it 

 is almost impossible to demonstrate the nature of the food stream 

 by means of basic dyes. More satisfactory results are obtained 

 after picro-acetic acid, but even with this, the food stream can 

 be made to take the acid stain. Similar staining reactions have 

 been observed by many workers in the case of other nucleins, 

 and Mann ('02), p. 339, in his criticism of A. Fischer's views, 

 gives a very good explanation of this behaviour. ' ' When there- 

 fore, Fischer observes nucleins to stain readily with basic dyes and 

 only after some delay with acid dyes, it means that the basophil 

 an-ion, nucleic acid, has its basic tendencies incompletely satis- 

 fied by the kat-ion albumen radical, and for this reason it readily 

 absorbes some more kat-ions, namely the color base. Conversely, 

 if the nucleic acid is not sufficient to satisfy the demand of the 

 kat-ion albumen, as is the case in those compounds which contain 

 only a little nucleic acid, then some more an-ions are attracted, 

 namely the color acid an-ions." The variations in staining 

 reaction therefore, are not to be taken as indicative of a purely 

 physical or rather mechanical, as opposed to a chemical union 

 between the dye and the substance dyed. 



The nutritive stream has undergone considerable change in 

 form since the preceding stage (Fig. 11). On entering the egg 

 (Fig. X) it now divides so as to enclose a more or less pear- 

 shaped portion containing the nucleus, leaving a narrow free 

 margin at the periphery of the egg. The granules are therefore 

 distributed in the form of an oval shell enclosing the yolk which 

 has begun to form in the center of the egg. 



Closer inspection of the cytoplasm shows a green-staining 

 reticulum having much coarser meshes than in earlier stages and 

 interspersed with granules from the food stream. In the photo- 

 graph the lighter areas show the regions where the reticulum is 

 practically free of granules. Fig. 33 represents a section where 

 the two zones adjoin. The food stuff spreads out along the lines 

 of the reticulum toward the center (to the left in the figure) and 

 the periphery (to the right) of the egg in the process of yolk 

 formation. In the course of this process, the granules disappear 



