CONTRIBUTIONS FROM THE CRYPTOGAMIC LABORATORY OF 

 HARVARD UNIVERSITY. — LXIII. 



ON THE CYTOLOGY OF THE ENTOMOPHTHORACEAE. 

 By Lincoln Ware Riddle. 



Presented by W. G. Farlow, May 9, 190G. Received May 14, 1906. 



Introduction. 



The Entomophthoraceae constitute a small, and, in some ways, 

 peculiar family of Phycomycetes, including, according to Schroeter's 

 arrangement in Engler & Prantl, seven genera. Of these seven genera, 

 we have more or less knowledge of the nuclear conditions in four. In 

 Conidiobolus (Brefeld, '84) we know only that the hyphae are non- 

 septate in the early stages, but in the older stages break up into 

 short sections (hyphal bodies) which are multi-nucleate. Basidiobolus 

 (Eidam, '87) is perhaps the best known of the genera from a cytological 

 point of view, chiefly on account of the work of Fairchild (97), although 

 the papers of Raciborski ('96), Lowenthal (:03), and Woycicki (:04) 

 are also to be mentioned. The hyphae are here septate, dividing the 

 fungus into cells, which are typically uni-nucleate ; the conidia also 

 possess single nuclei, derived directly without division from the parent- 

 cells. The zygospore is formed by the fusion of the nuclei of two 

 adjacent cells, this process being preceded, however, by the production 

 of two beaks on the fusing cells, with a simultaneous division of the 

 two gamete-nuclei so that a daughter-nucleus is cut off in each beak, 

 while the other two daughter-nuclei enter the young zygospore and 

 sooner or later fuse. Raciborski ('96") and Fairchild ('97) have both 

 described the division of the nucleus of Basidiobolus by a mitotic 

 method. 



The two remaining genera, upon which a certain amount of cyto- 

 logical work has been done, are Empusa and Entomophthora, all 

 the species of which are parasitic on the larvae, pupae, or imagines of 

 various insects, and resemble one another in their general life-history. 

 For the general morphology of these genera reference may be made to 

 the account given by Thaxter (88) in his monograph of the North 



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