692 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The sexual reprocluctive cells are formed on the thallus by the 

 differentiation of terminal cells of filaments. 



The male cells are usually collected in groups, constituting the 

 antheridia of various forms, exposed in the form of tufts, or buried in 

 depressions in the surface of the thallus. Within the autheridia are 

 formed the male fertilizing bodies or spermatia, usually of a si)herical 

 or elongated form, sometimes with a beak-like appendage ; they are 

 formed and discharged in succession. Although the author has been 

 unable at present to detect any spontaneous power of motion in these 

 spermatia, he does not consider the question altogether decided. 



The female sexual cells are always developed out of the terminal 

 cell of longer or shorter lateral branches. At the base of this female 

 cell or carpogonium is always formed the long hair-like appendage 

 known as the trichogyne. The ventral portion of the carpogonium 

 always incloses an abundant protoplasm, and sometimes chromato- 

 phores in addition ; the j)rotoplasm of the trichogyne is always 

 colourless. 



In impregnation the spermatia attach themselves to the apex of 

 the trichogyne, and at the same time clothe themselves with a cell- 

 wall. At the point of attachment the cell-wall of both spermatium, 

 and trichogyne is absorbed, and through this opening the contents of 

 the two coalesce ; the united protoplasmic mass contains at first two 

 distinct nuclei ; subsequently only one nucleus is to be found in the 

 carpogonium, probably from the coalescence of the two. The tricho- 

 gyne then becomes detached, and disapjiears. 



The impregnated carpogonium now divides into two cells of 

 unequal value ; the lower one only contains a nucleus, and is the 

 ovum-cell or oospore ; the upper one is functionless, and ultimately 

 disappears. The oospore does not, as is the case with the green alga3 

 and the higher cryptogams, become released from the tissue by which 

 it is surrounded, but remains closely associated with it ; sometimes it 

 is scarcely distinguishable, except in its power of development, from 

 an ordinary cell of the thallus. The mode of its develoj)ment varies 

 greatly in the different classes, and is described in detail. 



The simjdest mode of development of the cystocarp occurs in the 

 Helminthocladicfe, where a number of branches, the " ooblastema," 

 spring from the surface of the oospore ; this tuft of hairs may be 

 either exposed, or more or less concealed in the tissue ; in the cells 

 of these branches the carpospores are finally produced. In the 

 Gelidiese only a single ooblastcma-filament is produced, which enters 

 into intimate connection with the other cells of the fertile branch of 

 the thallus, deriving its nutriment from them ; the carpospores then 

 being formed in the cells of the fertile ooblastema-filament, which has 

 in the meantime branched abimdantly. The cystocarp, or mass of 

 fertile cells, forms a swelling within the fertile branch. In the 

 Cryptouemiofe and Squamarieoe (e. g. Duclresnaya) this process is 

 further modified by the fertile cells entering into actual communication 

 with certain special sterile cells, rich in protoplasm, through orifices 

 in their cell-walls ; the details of this conjugation with the so-called 

 " auxiliary colls " arc subject to groat variety in the different genera, 



