194 PROCEEDINGS OF THE AMERICAN ACADEMY. 



We may now sum up the line of development indicated in this paper. 



I. Sporodinia : Hyphae non-septate, with very numerous very small 

 nuclei. Non-sexual reproduction by a sporangium producing numerous 

 uni-nucleate spores. Resting-spore formed by the fusion of primitive 

 coenogametes with very numerous nuclei. Apogamy frequent. 



II. Empusa : Hyphae breaking into hyphal bodies with numerous 

 small nuclei irregularly distributed. Non-sexual reproduction by a 

 multi-nucleate "conidium" which is morphologically a coenocytic 

 sporangium. Apogamy constant. 



III. Entomophthora : Hyphae either breaking into hyphal bodies 

 after passing through a septate condition or else permanently septate, 

 with few large nuclei regularly spaced. Tendency toward nuclear 

 reduction extended to the non-sexual reproduction resulting in a uni- 

 nucleate coenosporangium. Resting-spores formed by the fusion of 

 primitive coenogametes with few nuclei. Apogamy occasional. 



IV. Basidiobolus : Hyphae septate, breaking into hyphal bodies 

 only under abnormal conditions, with a single nucleus in each cell. 

 Non-sexual reproduction as in Entomophthora. Resting-spores formed 

 by the fusion of coenogametes of a specialized type, which through 

 the extension of the tendency to nuclear-reduction have become 

 uni-nucleate. Apogamy absent. 



These three genera of Entomophthoraceae thus form a specialized 

 line, derived from a Mucor-like ancestry, and reaching a high stage in 

 the development of certain well-defined evolutionary tendencies. 



Summary. 



Material of the following species was studied during the present 

 investigation : Entomophthora Americana, E. " x," E. GeometraUs, E. 

 echinosjwra, E. rhizospora, E. Fresenii, and Empusa Grylli. 



The nucleus of Entomophthora shows a well-developed structure. 

 There is a relatively small chromatin-nucleolus surrounded by a more 

 or less dense zone of chromatin granules. The division of the nucleus 

 is by a well-developed process of mitosis. 



During mitosis, spherical chromosomes are organized by the direct 

 aggregation of the chromatin -granules, no spireme stage being present. 

 In E. Americana, eight chromosomes were counted with reasonable 

 certainty. 



The linin-fibres freed by this process of aggregation separate into 

 two groups which migrate to the respective poles of the nucleus, 

 forming a typical, intranuclear, bipolar spindle, without centrosomes. 



The conidia of Empusa are multi-nucleate, and of Entomophthora, 

 uni-nucleate. No nuclear-division is present in the process of 

 conidium-formation. 



