348 THE FRESH-WATER LOCHS OF SCOTLAND 
the second, third, and fourth spines were spreading, though not much 
so (Plate XV. fig. 13). 
On 11th May 1904, in Loch nan Eun, with a surface temperature 
of 52° Fahr., the forms were rather large and slender, the second and 
third spines long and divergent, whilst the fourth spine was wanting 
or ill developed (Plate XV. fig. 12). 
On 19th May 1904, in Loch nan Geireann (Mill), the surface 
temperature being 52° Fahr., the individuals were much like those 
of Loch Fiart. 
On 24th May 1904, in Loch Scadavay, the species was comparati\ ely 
large and slender ; the first, second, and third spines (especially the 
first) were elongated, but the fourth spine was ill developed (Plate 
XV. fig. 16). 
On 1st June 1904, in Loch Tormasad, at a temperature of 6S°'0 
Fahr., all the individuals were rather slender and long-spined ; but 
whilst most had no fourth spine, others had a well-developed one. 
On 3rd June 1904, in Loch Hunder, were rather large forms with 
elongated, wide-spreading arms, the fourth spine being moderately 
developed (Plate XV. fig. 11). 
On 6th June 1904, in Loch a' Bharpa, Ceratium was much the 
same as in Loch Hunder. 
On 18th June 1904, in Loch Hosta, the individuals were much like 
those of Loch F'iart. 
On 25th June 1904, in Loch a' Ghlinne-Dorcha, the surface tem- 
perature being 55'' '0 Fahr., the fourth spine was well developed, and 
the second, third, and fourth were wide-spreading and long. 
On the same date, in Loch Crogavat, at a temperature of 55° "2 
Fahr., the spines were long and slender, but the fourth spine was 
absent ; the same kind occurred in Loch an lasgaich on 9th June 
1904, at a temperature of 66° '0 F'ahr. 
On 1st July 1904, in Loch Ola vat (Benbecula), the individuals 
were rather small and the spines w^ere short, though the fourth was 
moderately developed. 
In the island of Lewis, Ceratium Mrund'mella w^as found in many 
lochs, but in no loch was it abundant. 
On 29th June 1903, in Loch Raonasgail, with a surface tempera- 
ture of 59° '0 Fahr., were found slender forms with elongated spines, 
but the fourth w as ill developed. 
On 17th July 1903, in Loch Langavat, the temperature being 
56°"1 Fahr., all the spines were long, the fourth being fairly well 
developed, and the second, third, and fourth spines were widely 
divergent (Plate XV. fig. 10). 
On 1st August 1903, in Loch Bodavat, the surface temperature 
being 60°-0 Fahr., the individuals were large ; all the spines were 
