\g2 KOTATOUIA 



little evidence that the liniitatit)ii of the algal llora in the higher lakes is one of the factors 

 involved, hut considerahly more data are required to suhstantiate tliis. 



It appears clear from the results of all investigators that the conmionot pelagic and 

 semipelagic rotifers of the high Aljjine ponds and lakes are Conocliiliis unkoniis, Euchlanis 

 dilatafa. Xofholca longispina and Polyarthra frigla. Zschokke concludes that the Alpine 

 rotatorian fauna is composed of widely distributed common species, a fact further empha- 

 sized by the list reproduced above. Pcdalia bulgarica appears to be the onl)- exception to this 

 generalisation. 



In no other part of the worUl have any relevant data been assembled. All the lakes 

 studied at high altitudes in N. America appear to lie lielow the timberline. Bryce (1931) 

 records 13 species from the sacred lake on Mt. Za(|uala in .\byssiiiia at an altitude of 2700 m. 

 (9000 ft.), but this locality clearly enjoys a temperate climate, and the same is true of Lake 

 Titicaca at an altitude of 3800 m. (12,500 ft.), from which Murray (1913) obtained ii 

 species. 



In comparing our list with that of the Rotatoria of the central European Alps it is 

 necessary to establish some sort of correlation between the ecological zonation in the two 

 areas. This raises considerable difficulties owing to the fact that the whole of Indian Tibet 

 enjoys a semi-arid climate and within the llimalaxan front-range no true forest occurs. 



The nival zone begins in the region studied at about 6000 m. Above 5000 m. larger 

 lakes such as Ororotse Tso and Togom Tso a])parently remain frozen for almost, if not 

 quite, the entire year. It is probably correct to regard the zone lying between 5000 and 

 6000 m. as the equivalent of the upper part of the subnival zone of the Alps. Thickets of 

 Salix sp. exist in sheltered valleys, such as the Nyagtsu valley North of the Panggong Tso, 

 up to 4600 m., but such rare and isolated thickets can hardly be regarded as representing the 

 upper limits of the forest zone of the Alps. Cultivation is carried on up to 4524 m. at 

 Phobrang, northwest of Panggong Tso and up to aljout 4540 ni. at Korzok on the shore 

 of Tso Moriri. The fields at the latter settlement are probably the highest cultivated land 

 in the world, but Francke (1914) gives evidence of former higher cultivation in this region. 

 It must, however, be remembered that owing to the poverty of the country and the isolation 

 of its communities agriculture is carried on under circumstances that would be economically 

 unremunerative in luirope. It seems, therefore, reasonable to suppose that the Al])ine zone 

 of the Alps is represented by the zone above 4500 m. though its upper limit is uncertain. 



In comparing oiu' list with that of the .\lps the data from above 1700 in. may therefore 

 be legitimately used, but the bdelloids and the attached forms (except Conocliiliis) must be 

 omitted, as our methods of study inevitably preclude their recognition. If this omission lie 

 made, the Alpine list is found to consist of 58 species, or just under three times the numl)er 

 recorded from the supposedly corresponding zones in Indian Tibet. When it i< rcmemljered 

 that the iVlpine list is the result of over fifty years' work by several investigators while our 

 list represents but a single season's collecting by one individual, it becomes prolialile that the 

 rotatorian fauna of Indian TilK't is at least as rich as that of the higher zones of the 

 mountains of Central Eurojic. 



Of the 21 species recorded in our list, 11 species arc found in the Alps above 1700 m. 

 and 7 species alx)ve 2300 m. Unfortunately these numbers are small ; an attempt was made 

 to determine if there is any correlation between the maximum altitude records of these 

 species in the Alps and in Indian Tiljet; the vahie of the correlation coefificient obtained, viz.. 



