RIDDLE. — ON THE CYTOLOGY OF THE ENTOMOPIITIIORACEAE. 185 



of fusion. This condition is comparable to that seen in the case of 

 Spicephal/'s nodosa (compare description by Thaxter, '97). 



In both of these methods, however, the essential cytological condi- 

 tions are the same. The two hyphal bodies fuse, the wall breaking 

 down between them, and the cytoplasm becoming completely con- 

 tinuous, so that no line of fusion is discernible. The wall near the 

 point of fusion, in the first case, or the wall of one of the hyphal bodies 

 at some other point, in the second case, then swells, and this swelling, 

 under the pressure of inflowing protoplasm, continues until a definite 

 ampulla is formed. The wall of this ampulla is only slightly thicker 

 than that of the hyphal body irom which it is derived, and forms, as 

 will presently be shown, the epispore of the zygote. Into this ampulla 

 pass all the nuclei of both the fusing hyphal bodies (see Figures 11-13). 

 It appears also that most, if not all, of the cytoplasm also passes into 

 the young zygospore. Figure 1 1 shows the much vacuolated cytoplasm 

 of the hyphal bodies ; and Figures 13 and 14 show young zygospores 

 attached to empty hyphal bodies. 



The fusing hyphal bodies are accordingly multi-nucleate structures, 

 the entire nuclear and cytoplasmic contents of which pass into the 

 young zygospore. The hyphal bodies are therefore strictly gametes, 

 and since they are multi-nucleate, are certainly to be considered coeno- 

 gametes. Since the coenogamete is a type of sexual organ which has 

 been shown by Davis (=00), Stevens (=01), and others to be character- 

 istic of the Phycomycetes, the establishment of its occurrence in the 

 Entomophthoraceae is a matter of great importance. 



After the entire contents of the two gametes have passed into the 

 young zygospore, the latter is cut off by a cross-wall. The exact 

 method of the formation of this wall has not been determined, but 

 stages, such as are shown in Figure 14, prove that the zygospore is not 

 abjuncted by a process of constriction, as is the case with the conidio- 

 spore. At this time the zygote is a spherical body surrounded by a 

 single thin wall. The cytoplasm is alveolar, and the relatively few 

 (probably not more than eighteen) large nuclei are irregularly placed, 

 with no apparent definiteness of arrangement. No fusion of these 

 nuclei has taken place up to this period of formation. 



The next process of interest in the development of the zygote is the 

 formation of the thick endospore wall. As has been mentioned above, 

 the epispore is derived directly from the wall of the hyj)hal body. The 

 endospore, however, does not appear until after the zygote is cut off by 

 a cross -wall and the old walls of the hyphal bodies have disappeared. 

 The first sign of the formation of the endospore is the marked increase 

 of vacuolation in a zone just inside the epispore (Figure 15). On the 



