19(36] Riddle, — Cytology of the Entomophthoraceae 67 



CONTRIBUTIONS TO THE CYTOLOGY OF THE 



ENTOMOPHTHORACEAE : PRELIMINARY 



COMMUNICATION. 



Lincoln Wake Riddle. 



For the past two years tiie writer has been engaged in a study of the 

 cytology of certain species of Empusa and of Entomophthora. One 

 species of Empusa and four species of Entomophthora have been ex- 

 amined. 



It has been found that the nucleus of Entomophthora has a highly 

 developed structure, showing little resemblance to the nucleus of the 

 Yeast, as Cavara suggested. Further the nucleus of Entomophthora 

 undergoes a more or less typical mitotic division. The resting- 

 nucleus shows a rather small nucleolus surrounded by a densely 

 granular chromatin-content, which may at times appear as a net- 

 work. During prophase the chromosomes (of which there are 8 in 

 E. Americana) are formed by the direct aggregation of the chromatin- 

 granules, without the intervention of a spireme-stage. This drawing 

 together of the chromatin leaves evident a number of linin-fibers, 

 running from the spherical chromosomes to the nuclear-wall which 

 persists throughout mitosis. These linin-fibers gradually separate 

 into two groups w^iicli draw toward the respective poles, forming 

 a typical, intranuclear bi-polar spindle. No centrosomes were seen 

 in any case. The so-called nucleolus appears to be strictly a kary- 

 osome, as it is identical with the chromosomes in appearance and 

 behavior during division. The later phases of mitosis are much as 

 in other cases. 



The nuclear details of zygospore-formation agree essentially with 

 those described by Gruber for Sporodinia; and the process in general 

 shows a close agreement with conditions in the Mucorales. The 

 zygospore either buds out at the point of fusion of the hyphal bodies 

 (compare the conditions in Piptocephalis) or else buds out from one 

 of the gametes (compare the conditions in SynccpliaUs nodosa). In 

 either case the fusing hyphal bodies are multinucleate structures and 

 are therefore coenogametes — a type of sexual organ shown by Davis 

 and others to be characteristic of the Phycomycetes. The entire 

 contents of both gametes, including all of the nuclei, pass into the 

 young zygospore. No fusion of the nuclei occurs during the first 



