54 Cytologie u. Befruchtung. 



Davis, BraDLEY Moore. Oogenesis in Saprolegnia. (Botanicat 

 Gazette. Vol. XXXV. 1903. p. 233—249, 320—349. 

 Pls. 9 — 10. — Published also in Decennial Publications, the 

 University of Chicago. Series I. Vol. X. 1903. p. 225— 257. 

 Pls. 15—16.) 



The study of oogenesis was made upon apogamous material 

 of Saprolegnia mlxta. The resting nucleus has essentialiy the 

 same structure as in the higher plants. In the coenocytic 

 oogonium there is one simultaneous mitosis, the spindles being 

 intranuclear. There are four chromosomes and no centrosomes. 

 The differentiation of egg origins (Anlagen) takes place around 

 coenocentra which exert a chemotactic influence upon the nuclei 

 in their vicinity. Generally one nucleus lies close to the coeno- 

 centrum and increases in size while all other nuclei in the egg 

 origin degenerate, so that eggs are usually uninucleate. Trinu- 

 cleate eggs are sometimes found and binucleate eggs are not 

 uncommon, but the binucleate condition need have no reiation 

 to sexuality. In the formation of eggs, the protoplasm collects 

 in denser masses about the coenocentra with their accompanying 

 nuclei. The protoplasm between the egg origins becomes less 

 dense and a series of vacuoles appear which separate the 

 origins from each other and allow them to round off as inde- 

 pendent eggs. 



The investigations upon sporogenesis resulted in a general 

 confirmation of the accounts of Rothert, Hartog and 

 H umph rey. 



More than half of the paper is devoted to a theoretical dis- 

 cussion of homologies and relationships among the Pliycomy- 

 cetes and Ascomycetes. The oogonia and antheridia of Pero- 

 nosporales, Saprolegiiiales, and Pyronema are the homologues 

 of gametangia and of the coenogametes of Mucorales. In the 

 evolution of the coenogamete, eggs with a larger number of 

 nuclei are regarded as more primitive, there being a tendency 

 to reduce the number of nuclei rather than the reverse. The 

 Mucorales, Peronosporales and Saprolegniales can be related 

 to each other only through a common ancestry whose sexual 

 Organs were coenogametes. The Ascomycetes may represent 

 two evolutionary lines derived from a primitive coenocytic type 

 of sexual organ (coenogamete). 



Charles J. Chamberlain (Chicago). 



Farmer, T. B., Moore, T. E. S. and Digby, C, On the 



cytology ofapogamyandapospory. I. Preliminary 

 note on apogamy. (Proceedings of the Royal Society. 

 Vol. LXXI. 1903. p. 453—457.) 



The cytological processes observed in one fern (Nephro- 

 diiim pseiido-mas. var. polydactyliim) are described. In the 

 prothallia binucleate cells occur, in regions corresponding with 

 those at which the apogamous outgrowths may be looked for. 



