78 4. Fortpüanzungslehre. 



duction a pairing of spirems is not necessary, but the cbromosomes instead 

 are arranged end to end in a spirem as in somatic mitoses. 



In the process of „double fertilization" in Angiosperms, tbe union of a 

 male cell with the endosperm nucleus is not considered to be a sexual act 

 but tbe subsequently developed endosperm is considered to be a part of the 

 female gametopbyte, just as a fern prothallium moy continue its growth after 

 the fertilization of its archegonia. 



The term parthenogenesis is limited to the development without fertili- 

 zation, of an egg having the reduced number of cbromosomes. 



The phenomena relating to graft hybrids or chimeras, and their sexual 

 offspring, lead to the view that fertilization and the transmission of cha- 

 racters are not accomplished by the protoplasm in general, but by the union of 

 specific material entities in the sexual nuclei. The writer concludes that the 

 „monopol" of transmitting hereditary characters belongs to the nucleus, in 

 which the characters are representecl by material entities, the chief function 

 of the cytoplasm being in its reponse to external Stimuli. 



Gates (St, Louis). 



205) Chamberlain, C. T., Nuclear phenomena of sexual reproduc- 

 tion in cymnosperma. 



(Ainer. Nat, 44,526. p. 595—603. 1910.) j 



The interesting stages of the reduction of the gametophytes are traced. 

 Beginning witb the ciliated sperms of the Cycads, the reduction of these 

 structures in the Conifer series, to male cells and finally male nuclei alone, 

 is shown. The prothallial cells and other features of the male gametopbyte 

 show a similar, though not always parallel, reduction series. Similarly in 

 oogenesis, the most primitive condition in Gymnosperma is soinewhat more 

 reduced than in Pteridophytes, since the archegonium never contains a neck 

 canal cell. Then the wall between the ventral canal nucleus and the egg 

 nucleus, is eliminated, and finally (Torreya) the division producing the ven- 

 tral canal nucleus is omitted. In Tumboa there is a further approach to the 

 Angiosperm condition through incomplete septation of the female gametopbyte, 

 and finally the archegonium is practically eliminated and we have free egg 

 nuclei without organized cytoplasm. 



The peculiar cytological conditions in the germ cells of Gymnosperms 

 are outlined, and the striking similarity of the early stages of the sporopbyte 

 to the female gametopbyte, is pointed out. This similarity results from the 

 closely similar conditions under which the two structures develope, and is 

 considered to be analogous to the similarity of the sporophytic and gameto- 

 phytic individuals of such Algae as Dictyota and Polysipbonia. 



Gates (St, Louis). 



206) Harper, R. A., Nuclear phenomena of sexual reproduction in 



F u n g i. 



(Amer. Nat. 44,525. p. 533—546. 1910.) 



The recent advances in the cytology of the Fungi are described in their 

 relation to the complicated life histories. The demonstration of sexualityin 

 many simple forms, including even the Yeasts, has shown the untenability of 

 the old idea that a parasitic mode of life tends to the disappearance of sexua- 

 lly. It is suggested that our conceptions of the sexual process may have to 

 be widened to include such phenomena as tbe fusion of the amoebulae to 

 form a Plasmodium in the Myxomycetes, for, altbough the cytological con- 

 ditions are imperfectly known, there is evidence of synapsis and reduction in 

 this group during spore formation. 



