THE ROTIFERA OF THE SCOTTISH LOCHS. 161 



Several other species were found which we failed to identify. 



The commonest animal in these deeper dredgings was Diglena uncinata. The 

 typical form of Dinocharis tetractis was rare ; but a variety, having the foot- spurs 

 nearly or quite obsolete, was abundant. Several forms of Eosphora differed more or 

 less from the types of the two species mentioned. 



There is little difficulty in accounting for the presence of these species at such depths. 

 They are all common along the shores of the loch. These shores in many places are 

 very steep, and it is easy to understand how animals which feed among the mud may 

 readily get deeper and deeper. They all feed on organic debris, and such food is 

 brought in abundance to these depths by the rivers, or falls down the steep slopes. 



In Loch Rannoch, Philodina macrostyla was dredged at a depth of 85 feet, but no 

 Rotifers were found in the greater depths of that loch. 



The abyssal region in Loch Ness can only be defined by negative characters ; it 

 lacks the majority of the littoral species. The littoral fauna gradually thins out as we 

 descend, till a certain depth is reached, beyond which only a few species survive, and 

 these extend to every part of the lake-bottom. Thus defined, we may say that there 

 are no abyssal Rotifers in Loch Ness, as no species extends all over the bottom, as do 

 Cyclops gig as, Pisidium, Candone, and the rest. 



As Dr Penard points out, in dealing with the Rhizopods (42), Scotland has many 

 other lakes, and we may yet discover in some of these the abyssal fauna and the 

 relict fauna of which we have as yet got no trace. Up to the present the indications 

 are against this expectation : north (in Loch Ness) and south (in St Mary's) there is the 

 same abyssal poverty. 



LIST OF SPECIES. 



Order RHIZOTA. 



Family Flosculariad.e. 



Floscularia campanulata, Dobie. Loch Ness. Floscularia mutabilis, Bolton. Loch Morar. 



,. ornata, Ehr. Stephanoceros eicJiJwrni, Ehr. Loch Ness, rare. 



„ pelagica, Kousselet (43). Widely dis- 



tributed. 



Family Melicertad^e. 



OEcistes crystallinus, Ehr. Loch Ness. Pseudcecistes rotifer, Stenroos (48). Loch Ness. 



„ brachiatus, Huds. Loch Ness (abundant), Conochilus volvox, Ehr. Generally distributed. 



Loch Tay. (j unicornis, Rousselet. Common everv- 



„ serpentinus, Gosse. Loch Ness, one ex- where. 



ample. 



