346 THE FRESH-WATER LOCHS OF SCOTLAND 
In Loch Suainaval, the deepest loch of Lewis, and also in Loch 
Stacsavat, which receives water from Loch Suainaval, the Bosmina 
was quite different from that found elsewhere ; it was rather larger, 
the mucro was very long, and so also was the rostrum ; the adults 
carried as many as twelve eggs each. It agrees with B. longispina, 
var. macrocerastes^ and is quite distinct from the long-spined forms 
of B. ohtusii'ostris. 
In North Uist and Benbecula the Bosmina was in general very 
like that of Lewis. In many lochs the adult specimens were some- 
what more elongated and the rostrum longer than in the Lewis lochs, 
but here too in the very oldest forms it was found that the rostrum 
shortened and the curvature of the dorsal contour increased ; further, 
with age the animal became more procumbent, in some few cases the 
mucro was much reduced — in Loch nan Geireann (Mill) the mucro 
was almost absent — but in most lochs it was of moderate size or 
long. The number of eggs carried by adults varied from two to 
seven. In some cases the head was almost as much depressed as in 
the var. procumhens. 
In the island of Mull the Bosmina of Loch Ba was distinctly 
different from that of Loch Frisa. The adults of Loch Ba were small, 
rounded forms carrying only one egg ; the dorsal contour was rounded, 
and the post-dorsal angle was quite absent, having merged in the 
curve of the back; the mucro was moderate-sized, the brow was not 
prominent, the rostrum was straight and of medium length. The 
young were more normal, being elongated, and having a definite post- 
dorsal angle (Plate XIV. figs. 5 and 6). On the other hand, the 
Bosmina of Loch Frisa was a larger form, the mucro was long, being 
occasionally though not usually serrated ventrally ; it was very like 
the ordinary forms from Lewis or North Uist. 
In the island of Lismore Bosmina was common in all three lochs. 
It belongs to exactly the same type as that of Lewis or North Uist. 
The young have rather longer spines than usual, and these are con- 
spicuously notched, but the notching is not found on the small mucro 
of the adult Bosmina (Plate XIV. figs. 7, 8, 9, and 10). 
In the Orkney and Shetland Islands Bosmina was rare ; in very 
few lochs was it at all common. The adult was of much the same 
type throughout the two areas ; it differs from that of Lewis mainly 
in size, being markedly smaller ; also the adult carries fewer eggs, 
usually one only, sometimes two, and rarely as many as four ; and 
further, the number of spines of the abdominal claw is always small, 
being only five. The young are elongated, the mucro is long, and the 
rostrum is long ; the adult is relatively shorter, the mucro is invariably 
short, the rostrum is short, sometimes v^ery short, the brow is pro- 
minent, and the eye moderate-sized or large. In sloughing specimens 
