1904 | LYON: EVOLUTION OF THE SEX ORGANS 291 
species of Lycopodium, notably Lycopodium annotinum (fig. 16), 
in which the antheridial region is made up of patches of 
spermatogenous cells quite indefinite in contour and varying in 
number. There is no wall of sterile cells. This appearance is 
not due to difference in state of development, or because 
antheridia are cut in different planes, as might be inferred from 
a single section. I have seen antheridia at maturity vary- 
ing in the number of sperm cells from fifty to more than three 
hundred. Not infrequently groups of spermatogenous cells 
derived from separate initial cells abut upon one another with no 
intervening cell tissue, but it is generally easy to trace the indi- 
vidual groups. Sex organs of this type are logically explicable 
by the progressive sterilization of an indefinite superficial region, 
but it requires a ‘our de force to imagine the modification of an 
emergent sporangium of definite form into the sunken condition 
displayed by Lycopodium. 
Archegonia and antheridia of few cells are generally regarded 
as the most advanced. From this standpoint, the sex organs of 
this species of Lycopodium are the most primitive ones known. 
This of course does not take into consideration the anomalous 
bisexual organs of Mnium cuspidatum described by Holferty. On 
the other hand, no gametophyte, with the exception of certain 
Mosses, is so complex in the variety and specialization of its 
vegetative tissues as that of Lycopodium complanatum or of Lycopo- 
dium annotinum. To be sure, the gametophyte of Lycopodium 
cernuum by contrast is exceedingly simple, and that of Phyllo- 
glossum is said by Thomas (13) to show little internal differentia- 
tion of cells; but cases are frequent among animals where somatic 
tissues become elaborate and highly organized, while the sex 
Organs lag behind and’ retain great simplicity. This would be 
expected in organisms where the struggle for existence is great, 
as it may have been among the Lycopodiums, if one may judge 
from the capricious germination of the spores. Moreover, the 
symbiotic relation of the club mosses with a fungus indicates 
difficulties in development. Attempts have been made repeatedly 
to germinate the spores of the club mosses, but the results obtained 
thus far have been unsatisfactory. The life history of every 
§ametophyte of Lycopodium now discovered is full of gaps. 
