915 
of Edinburgh, Session 1885-86. 
of the cell into a larger number of smaller spores, which settle down, 
however, and develop just like their more richly dowered neigh- 
bours. (2) In Ulothrix , again, both large and small spores may be 
formed by division, and both may simply come to rest and germi- 
nate. In such a case, however, the macrospores seem to form a 
weakly plant, unless they have previously united in pairs in con- 
jugation. (3) The reproduction of Ectocarpus is also effected by 
macro- and microspores, and in this case the latter generally though 
not invariably conjugate. Between the conjugating forms, more- 
over, a certain physiological difference can be detected ; some soon 
come to rest and settle down, and it is with these that their more 
energetic neighbours by-and-by conjugate. There is thus the 
beginning of a distinction between male and female elements. (4) 
Further, and more markedly, in Cutleria the two kinds of spores 
result from perfectly distinct sporangia, and the larger, less mobile 
macrospores, which soon come to rest, are fertilised by the smaller, 
more active microspores. Both the dimorphism and the fertilisa- 
tion characteristic of sexual reproduction have thus become, in a 
measure, defined. 
Let us now review these morphological facts in the light of pro- 
toplasmic processes. We see in Protococcus how spores of smaller 
size, that is to say, less predominantly anabolic, are yet able to 
develop independently ; and that this also happens with the 
microspores of Ulothrix, resulting, however, in a weaker plant, 
while a more successful development may be ensured by a process 
comparable to mutual nutrition. Individually they are too kata- 
bolic for anything but weak independent development ; in uniting, 
however, they are strong. The case of Ectocarpus is peculiarly 
instructive, not onl} T in the association of more marked microspores 
with the almost constant occurrence of fertilisation, but also in the 
presence of two distinct conjugating types, — the comparatively 
sluggish, more nutritive, preponderatingly anabolic (female) cells, 
which soon settle down, and the more mobile, finally more 
exhausted and emphatically katabolic (male) spores. In Cutleria 
too the less mobile and more anabolic macrospores are fertilised by 
the more active and more katabolic microspores, which have now 
gone too far for the possibility of independent development. 
In the Protozoa, also, amid the general occurrence of continuous 
