RIDDLE. — ON THE CYTOLOGY OF THE ENTOMOPIITIIORACEAE. 195 



The zygospores of Entomophthora are formed by the fusion of multi- 

 nucleate hyphal bodies, which are coenogametes of a primitive type, 

 since all of the nuclear material is retained in the zygote. No fusion 

 of the nuclei takes place during the first three months after formation. 

 Whether or not such fusion in pairs takes place at the time of germi- 

 nation it has been impossible to determine, owing to the difficulty of 

 germinating the zygospores under artificial conditions. 



The epispore of the zygote is derived directly from the walls of the 

 hyphal bodies. The endospore is formed by the direct transformation 

 of an outer zone of the cytoplasm of the zygote. 



In Empusa Grylli the azygospores are formed by the budding out 

 of a hyphal body. The entire nuclear and cytoplasmic contents of the 

 hjrphal body passes into the azygospore, which is therefore always 

 multi-nucleate. No division and no fusion of these takes place. 



The cytological evidence suggests the derivation of the Ento- 

 mophthoraceae from a Mucor-like ancestry, with the extension of the 

 coenocytic habit to the non-sexual methods of reproduction, and with 

 the progressive reduction in the number of nuclei, with the increasing 

 efficiency of the survivors, a process beginning in Empusa, carried 

 further in Entomophthora, and reaching its highest expression in 

 Basidiobolus. 



A preliminary notice of the results of the present study appeared 

 in Rhodora (Vol. 8, p. 67) on March 27, 1906. 



The writer takes this opportunity to make a grateful acknowledg- 

 ment of his indebtedness to Professor Roland Thaxter, under whom 

 the work was begun, for invaluable assistance in the collection of 

 material, and for much advice ; and to Professor W. G. Farlow, under 

 whom the work was finished, for help in the preparation of this 

 paper. 



Bibliography. 



Bail, Th. 



'69. Ueber Pilzepizootien der forstverheerenden Ranpen. Schriften d. 

 naturforsch. Gesel. Danzig, Vol. 2, pt. 2, pp. 1-25, pi. 1. 

 Brefeld, O. 



'84. Conidiobolus utriciilosus und C. minor n, spp. Untersuchungen aus 

 dem Gesammtgebiete Mykologie, Pt. 6, p. 35. 

 Cavara, F. 



'99*. I nuclei delle Entomophthoreae in ordine alia filogenesi di queste 



piante. Bull. Soc. bot. italiana (1899), pp. 55-60. 

 '99''. Osservazioni citologiche sulle Entomophthoreae. Nuovo Gioniale 

 botauico italiano, Vol. 6, pp. 411-4GG, pi. 4, 5. 



