i37 
Cytology and Classification. 
of its true affinities. We are least likely in the modifications of 
these organs to mistake a merely adaptive for an essential 
character.” Darwin adds, “ With plants how remarkable it is 
that the organs of vegetation, on which their nutrition and life 
depend, are of little signification ; whereas the organs of repro¬ 
duction, with their product the seed and embryo, are of paramount 
importance ! ” 
Amongst the Algae we meet with a really extraordinary variety 
in the structure and cytology of the sexual organs. To convince 
oneself of this it is only necessary to think of the differences 
between a few examples taken at random, such as the conjugation 
of Spirogyra, the oogonia and curious “ dwarf males ” of 
(Edogonium , the procarp, trichogyne, and spermatia of the red 
Algae, the oogonia and antheridia of Vaucheria, the biciliate 
gametes of Ulothrix, and the free naked eggs of the Fucaceae ! Two 
small sub-groups of the Algae, which are apparently by no means 
distantly related, may shew a degree of difference in their 
reproductive processes which among the higher plants would 
justify us in assigning them to altogether different divisions of the 
vegetable kingdom. As continually happens in thinking of any 
morphological subject we are again reminded of a passage in the 
Origin of Species. “ That the mere physiological importance of an 
organ does not determine its classificatory value, is almost proved 
by the fact, that in allied groups, in which the same organ, as we 
have every reason to suppose, has nearly the same physiological 
value, its classificatory value is widely different. As in 
most groups of animals, important organs, such as those for 
propelling the blood, or for aerating it, or those for propagating the 
race, are found nearly uniform, they are considered as highly 
serviceable in classification ; but in some groups all these, the 
most important vital organs, are found to offer characters of quite 
subordinate value. Thus .... in the same group of Crustaceans 
Cypridina is furnished with a heart, whilst in two closely allied 
genera, namely Cypris and Cytherea, there is no such organ ; one 
species of Cypridina has well-developed branchiae, whilst another 
species is destitute of them.” 
The sexual organs of the Fungi, in the cases where they occur 
and are functional, are distinquished from those of the Algae by a 
cytological character, the non motility of the sperm cells. As an 
instance of the treatment of a phylogenetic problem from a 
cytological stand point we may mention Mr. Blackman’s recent 
suggestion as to the affinities of the Uredineae which is based on 
