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1896] PROCARP AND CYSTOCARP OF PTILOTA 373 
likewise no evidence of fusion between the cells of the develop- 
ing cystocarps and the cells of any of the trichophoric appa- 
ratuses or the trichogynes. As is shown in all the figures, the 
cells of the cystocarp are separated from the trichophoric appa- 
ratuses by walls of considerable thickness, and cross-fusion of 
any sort certainly ought to have appeared in the sections. The 
fact that the sections were serial enabled the writer to examine 
all sides of the specimens, and would seem to have prevented the 
possibility of an ooblastema filament or fusion process escaping 
notice because it lay in such a plane that it could not appear in 
the median section. However, to guard against error of method 
the writer crushed out many of the young cystocarps in lactic 
acid, thus separating the procarps from the central developing 
cystocarp, and in such specimens saw no indication of an ooblas- 
tema filament. 
A satisfactory explanation of a sexual process in the case of 
Ptilota must then be one which answers the following question: 
viz., How can a sexual impulse be transmitted from a trichogyne 
to a carpogenous cell when the two structures are separated by 
a trichophoric apparatus of at least one cell (often more) through 
which the impulse must pass? From the literature it certainly 
seems as if the conditions above mentioned were essentially the 
same in the genera Callithamnion, Griffithsia, Ceramium, Sper- 
mothamnion, Spondylothamnion, and Lejolisia, but the writer 
Cannot in most cases speak from a personal study of the forms. 
Accepting the dictum that biology now lays down as to the 
fequirements of a sexual act, there must be a transmission of 
nuclear substance from the antherozoid through the trichogyne 
to the cells of the trichophoric apparatus, and thence on to the 
arpogenous cell. Any explanation of sexuality which satisfies 
the above condition must base its argument upon the fact of 
there being a continuous mass of protoplasmic matter from the 
trichogy he to the carpogenous cell, because of strands of 
protoplasm connecting the cells one with another. 
The difficulties that a satisfactory hypothesis must 
come, even though it rest on the above mentioned fact of an 
over- 
