THE STRUCTURE OF PROTOPLASM. 15 



with granules, i.e., drops, of all sizes, ranging from the smallest 

 visible ones up to the largest alveoli. It is this fact which Mrs. 

 Andrews, as I understand her statements, has in view in main- 

 taining that the coarser alveolar structure " is not indeed the 

 final structure of the living substance, but is part only of an 

 infinitely graded series of vesiculations of the protoplasmic 

 foam" ('97, p. 12), and with this statement I entirely agree. 

 But we cannot stop here. Irresistibly the further question 

 suggests itself : Why should we place the end of this series at 

 the end of microscopical vision under a 1.5 mm. immersion 

 objective which is of course a perfectly arbitrary and arti- 

 ficial limit? It is impossible to doubt that powers still higher 

 than any at our command would reveal the existence of granules 

 still smaller, and that what appears as " continuous " or "homo- 

 geneous " substance is itself an emulsion beyond the range of 

 vision. 



We may now inquire whether the coarser visible alveolar 

 structure is characteristic of all protoplasm. This question 

 has in a measure already been answered, for in these very eggs 

 we have seen the alveolar structure giving rise to a fibrillar one 

 in the aster-formation in other words, the protoplasm of the 

 same cell may in different phases pass back and forth from one 

 state into another. This fact appears in its clearest form when 

 we study the growth of the ovarian ova, which gives us many 

 additional suggestions of high interest. The entire coarser 

 alveolar structure, as described above, i.e., the foam-structure 

 of Biltschli, is in these eggs of secondary origin. The very 

 young living ovarian eggs consist of "homogeneous" proto- 

 plasm, such as has been described by many botanists in the 

 embryonic tissue-cells, through which are irregularly scattered 

 a few small spheres and many excessively small granules. As 

 growth proceeds, both the spheres and the granules increase in 

 size, the latter enlarging to form new spheres, while new gran- 

 ules continually emerge from the protoplasmic background into 

 the limits of vision. In the middle stages of growth, the proto- 

 plasm is thus converted into an emulsion, being filled with 

 spheres of all sizes, ranging downwards from i.o micron to 

 the smallest granules, but still showing no regular arrangement 



