370 MR. G. S. WEST ON 
probably more striking than those shown by any living 
vegetable organisms of more complex character. Although 
merely unicellular organisms, major and minor symmetries are 
observed to play a prominent part in the construction of exquisite 
patterns; and the question of the “ significance of pattern” in 
these beautiful little plants is therefore one of deep interest. The 
complexity of outline so characteristic of the majority of Desmids 
has been stated to have been developed in all probability during 
tle gradual evolution of the Desmid-forms from the original 
filamentous Conjugates with cylindrical cells, the loss of the 
filamentous condition necessitating the development of some 
other protective characters. The acquirement by the unicell of 
these protective charaeters— protective not only against the de- 
predations of small aquatic animals, but also in part protective as 
anchors in time of floods—has resulted in the division into lobes 
and often into toothed lobules, sometimes accompanied by a 
flattening of the cell, and at other times by the development 
of processes of multiform character, or of spines, warts, or 
other protuberanees. There is a Law of Symmetry recog- 
nizable in all living objects, a visible token of the law and 
order which everywhere accompany vital phenomena: and in 
the acquirement of these wonderfully varied features and useful 
characters by this specialized family of plants this Law of 
Symmetry has exercised its full influence, resulting in the pro- 
duetion of the exquisite patterns that are often met with. 
The presence of major and minor symmetries is most distinctly 
evident in some species of Micrasterias, in which it often happens 
that only the corresponding lateral lobules agree in the extent 
of their subdivision ; efr. b, b in fig. 1 (p. 371). Another proof 
of this is found in the extraordinary variation sometimes met 
with in the corresponding lobules on each side of a semicell ; 
cfr. a, a’ in fig. 1. 
In commenting on Cosmarium pileigerum, Lagerh., and some 
varieties of C. pseudotaxichondrum, Nordst.,* the late Rev. 
Francis Wolle somewhat hastily states t that * G. v. Lagerheim 
appears to give too much prominence to simple differentiations— 
mere vagaries of the same species.” I have examined large numbers 
* Vide Q. v. Lagerheim, * Bidrag till Amerikas Desmidie-flora,’ Ofvers. af 
K. Sy. Vet.-Akad. Förh. 1885, no, 7, p. 258. 
t F. Wolle, Freshw. Alg. of the United States, 1887, p. 22. 
