KOTA-IOUIA 183 



0.19, is (juite without signilicaiice wlien derived Irmn eleven pairs of ol)servations. While 

 it is clear that there are considerable similarities between the two faunae, evidence not sus- 

 ceptible to statistical treatment strongly indicates that there are also differences l^etween 

 them, lor it is to be noted that of the four commonest Alpine free-swimming rotifers only 

 one, Polyarthra trigla, occurs in our list for over 4500 m., and that Notholca longispina, 

 perhaps the commonest Alpine species, and Coiiocliilus uiiicoiiiis, were found nowhere in the 

 regions studied. 



With the exception of Pcdalia bitlgarica, all the species that we record have previously 

 l)een found at about sea-level in widely distant countries, and in general our list supports 

 Zschokke's conclusion that the .Vlpine rotatoria are predominantly eurytopic species of 

 immense vertical and horizontal distribution. Bearing in mind the differences that we have 

 just noted Ijetween the fauna of the Alps and that of Indian Tibet, it is safe to conclude 

 that the rotifer fauna of very elevated waters represents, with the single exception of P. 

 bulgarica, a remnant of the common, and in general eurytopic, fauna widely distributed 

 throughout the earth, but that the composition of this remnant differs from place to place, 

 such differences l^eing perhaps in part due to chance and in part due to ecological factors, 

 of which latter the occurrence of Brachionus plicatilis provides an extreme example. 



Pcdalia bulgarica has been mentioned so often throughout this discussion that a few words 

 as to its ecology may be appropriate. The species was met with in three localities. 



As indicated above, a number of well-preserved specimens were obtained from two of 

 the Togarma Tso ponds; these were determined by Dr. W^iszniewski. A single specimen 

 was obtained in one of a similar series of ponds at Chushol (altitude 4336 m.) and several 

 very poorly preserved specimens from the open water of Pangur Tso (altitude 4329 m. ) 

 were found to be undoubtedly referable to this species on account of the absence of posterior 

 appendices and the six teeth of the uncus. None of these waters were very cold at the time 

 when the material was collected. At Togarma Tso there was undoubtedly a great diurnal 

 variation in temperature, but in Pangur Tso, the temperature lay between 15.1°C., 

 (surface) and 14.2'C. (9 meters) on 13 August and 14.1°C. (surface) and 13.8"C. (9 

 meters) on 14 August, so that in this locality the species must l)e continually exposed to a 

 moderate temperature of about 14°C. in the summer. The record of the species in Pangur 

 Tso is also of interest as indicating that it is tolerant of considerable alkalinity (alkali reserve 

 0.0610 N., chloride 0.022 N., pH c. 9.6). These facts are of interest as indicating that 

 this species, the only recorded alpoliiont rotifer, is more tolerant of diverse conditions than 

 might be expected. 



Osborn Zoological Laboratory of Yale University, 

 23 July, 1934. 



