254 RESEARCH SEMINAR. 



The conceptacle of Sargassum originates with a single super- 

 ficial cell. Cell division beginning in this initial continues in the 

 progeny until the conceptacle is formed. The entire organ, there- 

 fore, is the descendant of one cell, the true initial. 



The antheridium and oogonium develop from wall cells of the 

 conceptacle as in other members of this group. The oogonium 

 has no pedicel, however, and usually contains but one egg. 



The cryptostoma develops from a single superficial cell as does 

 the conceptacle and is homologous with that organ. 



July 22. Cytological Studies on Nemalion. By DR. JAMES J. 

 WOLFE. 



The chromatophore of N'emalion has a hollow ellipsoid form from 

 which processes radiate to the periphery of the cell and there 

 flatten out to form a clathrate membrane. The region surrounded 

 by the ellipsoid portion of the chromatophore, and generally re- 

 garded as a pyrenoid, consists entirely of vacuolar material. 



The sex-organs cannot be regarded as unicellular structures ; 

 since in earlier stages the trichogyne possesses a well organized 

 nucleus, which fragments as that organ matures ; the egg-cell 

 thus becoming an intercalary cell, and the trichogyne one which 

 has been specialized in connection with the reproductive processes. 



The nucleus of the spermatium normally divides into two fer- 

 tilizing elements which are discharged into the trichogyne ; which 

 events show the so-called spermatium to be an antheridium. 



In the mature cystocarp the ultimate cells give rise terminally, 

 as well as by subterminal proliferation, to a variable number of 

 carpospores, which is further augmented by repeated proliferation 

 within the successively formed mother-cell walls. 



The entire chromatin content of the nucleus is stored in the 

 nucleolus, and in the prophases of division passes to the nuclear 

 wall along delicate fibrillae. The spindle is intranuclear, and 

 centrosomes are distinctly visible at metaphase. 



The conclusion that NemaHon presents the essentials of an 

 antithetic alternation of generations, and that the cystocarp is, 

 therefore, the homologue of the sphorophyte in higher plants, is 

 indicated by cytological evidence -- since approximately sixteen 

 chromosomes are present in the divisions of the cells of the cysto- 



