RIDDLE. — ON THE CYTOLOGY OF THE ENTOMOPIITUORACEAE. 183 



draw apart (Figure 10), giving a very characteristic dumbbell-shaped 

 appearance, similar to that figured by Stevens (: 01) in Albugo. The 

 entire wall of the daughter-nuclei in this case would be formed from 

 the wall of the mother-nucleus. Whichever method is followed, the 

 daughter-chromosomes remain more or less visible until after the wall 

 is completed, when they fragment and become redistributed in the form 

 of granules. Owing to the smaller size of the nuclei and to the den- 

 sity of their contents and to their strong affinity for stains at this 

 time, it was found impossible to follow the process in detaih But it 

 is not improbable that the process is the reverse of that followed in 

 the organization of the chromosomes, in which case the fragmentation 

 would be accompanied by a redistribution of the chromatin over the 

 persistent linin-fibres. 



To sum up : the process of mitosis in Entomophthora shows a chro- 

 matin-nucleolus ; an organization of chromosomes by the aggregation 

 of granules, without the intervention of a spireme-stage ; the forma- 

 tion of a typical, intranuclear, bipolar spindle, without centrosomes, 

 directly from the linin-fibres, which retain their connection wath the 

 chrosomomes throughout mitosis ; and, in the daughter-nuclei, a redis- 

 tribution of the chromosomes in a granular form over these fibres.^ 



Conidia. 



The conidia of the following species have been examined and found 

 to agree in the essential details : E. Americana, E. Geotnetralis, E. 

 echinoapora, E. rhizospora, E. Fresenii As an illustration of the devel- 

 opment and structure of the conidia in these species, the process may 

 be described as seen in E. Geometralis. 



About the time of the death of the host the hyphae break up into 

 short multi-nucleate portions known as hyphal bodies (Thaxter, '88). 

 The young hyphal body is a thin-walled structure, the cytoplasm of 



>■ Since tlie completion of this worii, two papers have appeared by E. W. Olive, 

 under the general title, " Cytological Studies on the Entomophthoreae " (Botani- 

 cal Gazette, 41, 192-205 and 229-258, with pis. 14-16). The first paper presents 

 a discussion of certain points in the life-history of various species of Empusa, 

 in particular a new species, E. Sciarae, with a general confirmation of the results 

 of previous workers in regard to the details of conidium formation. The second 

 paper discusses cell- and nuclear-division. Olive finds tliat cell-division takes place 

 through the entrance of a ring-shaped cleavage-furrow. The account of nuclear- 

 division is in striking contrast to the conditions seen in the course of the present 

 investigations, so mucli so that a close comparison is impossible. Olive describes 

 what he calls a " primitive mitosis " resembling that of the lower Protozoa, a pro- 

 cess controlled by " intranuclear centrosomes " and without definitely organized 

 chromosomes. 



