190 PROCEEDINGS OF THE AMERICAN ACADEMY, 



azygospore is a multi-nucleate structure ; and the attached empty 

 Lyphal body together with the absence of a cross-wall proves that this 

 multi-nucleate condition is brought about, not by the successive divi- 

 sions of a single primordial nucleus, but rather by the inclusion in the 

 azygospore of the entire number of nuclei which were present in the hy- 

 phal body. As this number is, within certain limits, somewhat variable, 

 the number of nuclei in the azygospore is correspondingly variable. 



The next stage in the formation of the azygospore is marked by the 

 formation of a cross-wall, cutting off the recently formed resting-spore ; 

 this being immediately followed by the dissolution of the walls of the 

 empty hyphal body leaving the rounded azygospore, which at first 

 often shows the position of the cross-wall (Figure 28). The cytoplasm 

 is reticulated in structure, the meshes being comparatively small, and 

 clearly granular ; the wall is still only slightly thicker than that of the 

 hyphal body, but the thickening process begins immediately. 



An additional piece of evidence against the occurrence of nuclear- 

 division within the azygospore is the fact that all of the stages de- 

 scribed above, from the first sign of a small protuberance up to the 

 fully formed spore, may be found on a single slide. Preparations of 

 material in which the spores had been formed from one to several days 

 were also studied. Yet in no case was there the slightest evidence of 

 nuclear- divisions. Further, the number shows no striking variation, 

 although it is often difficult to follow a spore through all the succes- 

 sive sections in which it should appear ; and, likewise, there is no 

 marked diminution in the size of the nuclei, such as would take place 

 during nuclear-division (as is shown by comparing the mother-nucleus 

 with the daughter-nuclei in Figures 1 to 10). 



Finally, preparations were made firom azygospores, three months old 

 at the time of fixation. A median section of one of these is shown 

 in Figure 29. The thinness of the wall in this case is anomalous and 

 difficult to explain, since the normal procedure is for the wall to 

 thicken immediately after the formation of the cross-wall, the mature 

 azygospore having a thick wall with epispore and eudospore differen- 

 tiated similar to that described for Entomophthora. The appearance 

 of this spore, fixed three months after formation (Figure 29), will be 

 seen to be clearly similar to that of the newly-formed spore (Figure 

 28). The spore has increased in size somewhat, but with a corre- 

 sponding increase in the vacuolation of the cytoplasm, these vacuoles 

 being filled, in the living material, with oil-globules. The nuclear con- 

 ditions are essentially identical with those in the young azygospore, 

 and show clearly that no nuclear-divisions, and, likewise, no nuclear- 

 fusions, have taken place up to this time. 



