510 MR W. WEST AND MR G. S. WEST ON 
than half—consists of Chlorophycez, and most of these green Aloz belong to the 
Conjugate. Slender species of Spirogyra, Zygnema, and Mougeotia occur in abund- 
ance in the plankton of many of the lochs, and the filaments of Mougeotia are particu- 
larly conspicuous. These species appear to rarely conjugate in the plankton, and they 
are most likely replenished from the shores of the lochs and by the streams draining — 
more elevated boggy areas. Some of the filaments of Mougeotia become greatly coiled — 
and contorted, presenting an appearance which we have never observed in specimens _ 
from any other situations. Zygnema ericetorum sometimes occurs in sufficient quantity — 
to attract attention. i 
As we have previously pointed out, the Scottish plankton is unique in the abund-— 
ance of its Desmids. The richness of its Desmid-flora is at once the most conspicuous _ 
feature of the plankton. = 
Some of the Desmids which are characteristic of this western area of Scotland are 
more abundant in the plankton of the lakes than in any other situations. To these ; 
must be added a number of Desmids which have hitherto only been found in the 
plankton. The following species can be regarded, so far as Scotland is concerned, as — 
true plankton Desmids, being more abundant in the pelagic region of the lochs than in~ 
any other situations :— 
Gonatozygon monotcenium. Staurastrum grande. 
Genicularia elegans. a brevispinum and several varieties, 
Clostertum Kiitzingit. Bs lunatum, var. planctonicum. 
ELuastrum verrucosum, vars. reductum and 5 aversum. 
planctonicum. 3 subnudrbrachiatum. 
Micrasterias Wallicha. teliferum. 
Cosmarium contractum. ra erasum. 
' depressum, var. achondrum. 5 pseudopelagicum. 
abbreviatum, var. planctonicum. "1 paradoxum and varieties (espe- 
” 
Xanthidium antilopeum and a number of cially var. longipes). 
varieties. » gracile and varieties. 
- subhastiferum. 5 anatinum and a number of 
hs controversum, var, planctonicum. varieties (especially var, 
Arthrodesmus Incus, and several varieties. grande). 
As quiriferus, ¥ Ophiura. 
‘i Crassus. * Surcigerum. 
5 triangularis, var. subtriangularis. * sexangulare. 
Staurastrum dejectum, var. inflatum. e Arctiscon. 
3 curvatum. Spondylosium pulchrum, var. planum. 
a jaculiferum and varieties. Desmidium graciliceps. 
ys megacanthum and var. Scoticum. 55 coarctatum, var. cambricum. 
i cuspidatum, var. maximum. 3 occidentale, 
i imelegans. Hyalotheca mucosa, 
- longispinum and var. bidentatum. 
“ Brasiliense, var. Lundellit, 
rt neglecta, 
Some of these Desmids develop very large mucous investments, and others are 
remarkable for the length and strength of their spines. 
We call attention here to the abundance of Mesoteniwm macrococcum in certain 
