Lewis.— The Life History of Grijfthsia Bornetiana . 679 
constitute a generation similar to the sporophyte of the Archegoniate series. 
Later ( 59 , ii), he elaborated this conception and expressed the opinion that 
the sporophyte is of antithetic origin, i. e. that it became gradually inter- 
calated in the life-history by a series of stages of increasing complexity. 
In those forms in which the tetraspores are borne on distinct plants, he 
regards the tetraspore-producing plant as a ‘facultative gametophyte’, which 
is a result of a process of differentiation similar to that which produced 
dioecism in many of the Archegoniates. The tetraspores he considers 
analogous to the gemmae of certain liverworts. Admitting the possibility 
that a numerical reduction of the chromosomes may take place in the 
tetrasporangium, he expresses the opinion that the number of chromosomes 
is not the final test of alternation of generations. ‘ Ich vermute, die 
vergleichende Untersuchung des ganzen Entwickelungsganges fiihrt eher 
zum Ziel, oder aber die Kombination beider Methoden ’ ( 59 , ii, p. 273). 
The work of Wolfe on Nemalion multijidum ( 90 ), in which he found 
a numerical reduction of chromosomes just previous to the production of 
carpospores, furnished a cytological analogy between the cystocarp of the 
Rhodophyceae and the sporogonium of the Bryophytes, and strengthened 
the position of Oltmanns. 
Yamanouchi ( 93 ), after a very complete cytological study of Poly - 
siphonia violacea , reached the following conclusion : ‘ The sexual plants and 
the tetrasporic plants present the two distinct phases of an antithetic 
alternation of generations, with the cystocarp a part of the sporophytic 
phase ’ (p. 433). This conclusion is based on the discovery by Yamanouchi 
that the dividing nuclei of the tetraspore-producing plant throughout its 
history, as well as those of the sporogenous cells of the cystocarp, show 
forty chromosomes (the %x number), while the nuclei of the sexual plants show 
twenty chromosomes (the x number). The number of the chromosomes is 
reduced in the divisions of the nucleus of the tetraspore-mother-cell ; the 
double number is restored by the union of the nuclei of the gametes. In 
discussing the origin of the tetraspore, Yamanouchi surmises that in some 
such form as Batrachospermum , in which monospores are borne along with 
gametes on the sexual plants, reduction may have been suppressed in the 
formation of the carpospore, ‘ so that it germinates with the sporophytic 
number of chromosomes, producing a plant which consequently becomes 
at once a part of the sporophytic phase. It is quite possible that the 
first tetraspore-mother-cells corresponded to monospores on the sexual 
plant, except that they had the double number of chromosomes, since such 
reproductive cells would very naturally become the seat of the delayed 
reduction phenomena. The resemblance in general morphology of the 
tetrasporic plants in the red algae to the sexual plants would be expected 
because they live under similar environmental conditions ’ (p. 435). 
The views of Oltmanns and Yamanouchi coincide so far as regarding 
