192 PROCEEDINQS OF THE AMERICAN ACADEMY. 



myc^tes au niveau des Empusa. Les details publies par Cavara sur la 

 structure de Y Empusa Muscae, details que j'ai pleinement v^rifi^s, 

 montrent clairement ce dernier stade de revolution apocytique des 

 appareils vdg^tatif et conidien des Entomophthordes." Vuillemin 

 thus makes Basidiobolus the primitive form for the family. But such 

 a primitive form should show some points of relationship to the forms 

 from which it has itself been derived. These points further should 

 be shown in connection with the sexual processes, the period of the 

 life-history, which is generally agreed to be of the greatest phylogenetic 

 importance. In connection with his views Vuillemin offers no special 

 form to which Basidiobolus might be directly related. 



Such a line of evolution, as Vuillemin suggests, has been discussed 

 by Davis (: 30) in connection with his consideration of the origin and 

 evolution of the coenogamete. Davis says : "It is conceivable that 

 a uni-nucleate sexual element might become multi-nucleate perhaps 

 through such an increase in the protoplasmic content that more than 

 one nucleus would be required to control satisfactorily its activities. 

 This possibility has absolutely no evidence in its support. There is 

 no series of forms whose sexual cells pass from a uni-nucleate condition 

 to a multi-nucleate. There are no indications that such an evolutionary 

 process has ever taken place among plants." 



So much for negative evidence against such a process as Vuillemin 

 supposes to have occurred. Let us now see what positive evidence 

 there is for the second of the two views stated above. The most 

 interesting piece of such evidence, because the most complete, is that 

 of the Albugo series established by Stevens ( :01) (and also quoted by 

 Davis (1. c.) ). Here the progressive increase in the development of 

 the physiologically important coenocentrum, and the corresponding 

 decrease in the now functionless receptive papilla indicate clearly the 

 line of evolutionary advance. While along with this, we have a pro- 

 gressive reduction in the nuclei, starting with Albugo Blltl with many 

 functional gamete-nuclei, through A. Tragopogonis with many poten- 

 tial but only a few functional, and ending with A. Candida, with its 

 single functional gamete-nucleus. This view may now be applied to 

 the conditions in the three genera of the Entomophthoraceae. 



In Empusa, the originally non -septate hyphae early break up into 

 short segments, the hyjihal bodies, which contain large numbers of 

 small nuclei distributed irregularly through the plasm. The conidia 

 are multi-nucleate. A large number of nuclei enter the apogamous 

 resting-spore. In Entomophthora the hyphae usually break up into 

 hyphal bodies, but as has been shown above in the case of JJ. (u'onicfrcdls 

 and as Cavara has shown in E. IJi'lpiniana, the formation of hyphal 



