530 FOOT AND STROBELL. [Vol. XVII. 



areas of cytoplasm which appear to be entirely free from 

 archoplasm, these areas showing a network structure which is 

 typical (at least after fixation). This appears to indicate 

 that the archoplasm is not necessary to the formation of 

 the typical network and is thus an individual constituent, 

 which may combine more or less intimately with the other 

 constituents of the cytoplasm. We claim merely to be able 

 to demonstrate a morphological dissimilarity of the two sub- 

 stances (as they appear in fixed material), and we hope to 

 illustrate with our complete series of photos the presence of 

 the archoplasm during all stages of the development of the 

 Q%g, and each step of the final aggregation of part of it to 

 the poles of the mature, fertilized tgg. The continuity of 

 the substance is so complete that we do not feel justified in 

 giving it another name at any one stage of the development 

 of the tgg (Pis. XLI, XLIII, XLIV). 



TecJiniqiie. — The technical manipulation of the cocoon 

 eggs has been described in an earlier paper (lo). The 

 ovaries were vivisected and dropped immediately into the 

 fixing fluid, the time required for the removal of the ovaries 

 from the living worm averaging about five minutes. The 

 fixative for each subject is noted under the explanation of 

 the photographs. • 



Study of the Living Ovaries. — Since first studying the 

 living ovarian eggs (1894) the observations have been repeatedly 

 renewed, these proving a valuable control for fixed material, 

 but beyond this being of little practical value. Even with 

 the aid of a Zeiss 2 mm. immer. lens, eggs are very rarely 

 found in which the yolk-nucleus can be recognized. In many 

 of the smaller cells, however, a differentiated area can be 

 distinguished close to the nucleus, and this corresponds in 

 size and position to the archoplasm (yolk-nucleus) seen in 

 fixed material. Munson (24), PL XIII, Fig. 16^, shows a 

 differentiated area in the living ovarian 0.^2, of Limulus, 

 which he describes as granular, but this area in Allolobophora 

 appears to be clear and homogeneous. In the living %^g the 

 membranes of the ^^2, and of the germinal vesicle can always 

 be seen distinctly, but a nucleolus is the only constituent of 



