52 JAMES MURRAY 



giown to show definite structures (such as the teeth) all of them were in the same 

 degree of advancement, as far as could be perceived. This is different from what is 

 the case in the genus Rotifer, in which all the species are viviparous. There the 

 two or three embryos are at different stages. The yolk-mass, which could rarely be 

 seen, contained eight nuclei. On one occasion (March 27, 1908) a yolk-mass was. 

 seen divided up into six portions, each containing a nucleus, no doubt a brood at an 

 early stage. Three pairs of narrow spindle-shaped vibratile tags have been seen. 



Habits. A. grandis has not the restlessness which is characteristic of the genus. 

 It is sufficiently active, but it creeps steadily, and "right side up," like many of the 

 Philodinadse, and can therefore be more easily studied. It feeds on minute organic 

 particles, among which there is rarely any recognisable organism. 



Habitat. Among the brown vegetation in the lakes at Cape Royds. It was the 

 most generally distributed of all the Antarctic rotifers, and occurred in saline lakes 

 from which most of the other species were absent. 



Natural history. A detailed study of Adineta grandis will be made in another 

 paper.* A summary of the ascertained facts will be here given. The species is the 

 only rival to Philodina gregaria in abundance, and in this connection it is important 

 to note that it shares with it the viviparous mode of reproduction. It is found in a 

 greater number of lakes than P. gregaria, but it never appears to be in such 

 prodigious numbers. This may be due merely to its less conspicious colouring, which 

 is almost identical with that of the plant on which it lives. 



It is not extremely abundant in the freshwater lakes, where it has many com- 

 petitors, but in the very saline Green Lake, from which all the other species but 

 Callidina constricta are absent, it is almost as abundant as P. gregaria is in Coast 

 Lake, and may be collected in the same way. When the fine debris washed from 

 the weed of Green Lake is allowed to stand undisturbed for some hours a pale brown 

 layer appears on the surface. This may be taken up by the pipette and is found to 

 be pure Adineta grandis, without admixture of other organisms. The rotifer has 

 crept out of the mud to the surface. This habit allows quantities to be got for study 

 and makes it easy to make simple experiments upon them. It did not usually creep 

 up the sides of the bottle, as P. gregaria does, but on one occasion, when a moderate 

 number were mixed with that species, they also crept to the surface of the water. 

 They could be obtained at any time during the winter by melting some ice from 

 Green Lake enclosing some of the brown weed. They usually began to move as soon 

 as released. 



In its power to endure extreme changes of temperature and other adverse 

 conditions, Adineta grandis is the most interesting of the Antarctic rotifers. From 

 its large size and great abundance, it was the species selected for most of the experi- 

 ments made with the object of finding the limits to the vitality of Rotifers. It 

 survived the lowest temperatures experienced at Cape Royds ( - 40 F.), and repeated 



* On " Life under Polar Conditions." 



