431 



IYOTE ON TETRAMASTIX OPOLIENSIS (ZACHARIAS). 



By Charles F. Rousselet, F.R.M.S. 



{Bead October 19U, 1906.) 



Plate 34. 



In my recently published paper on South African Rotifi ra * I 

 mentioned having found this rare species in a pool of a streamlet 

 in the Matopo Hills, Rhodesia. My specimens had to be pre- 

 served without examination, so that they were not seen alive, 

 but were found afterwards in the collected material in a fully 

 contracted state. I mentioned that on the occasion of its first 

 discovery by Dr. O. Zacharias in 1897, Tetramastix opolieasis 

 was also found fully retracted in preserved material from the 

 River Oder, near Oppeln, in Upper Silesia, Germany, and that 

 no one had vet seen this rotifer in the living state 



After the publication of ray paper I received a note from Herr 

 Stanislas Hlava, of Prag, who informed me that he had found 

 Tetramastix in September, 1899, in a small pond near Tabor, in 

 Bohemia, when examining plankton of ponds as a student. The 

 species occurred in great abundance then, but has not been seen 

 there since. Fortunately Mr. lilava made a very good sketch 

 of the living animal, which he has been good enough to allow me 

 to publish in our Journal, and which entirely changes our notion 

 of the affinities of this species. 



It will be seen at once from this drawing (Plate 34, Fig. 1) 

 that, instead of being allied to Notholca longispina, ;ts was sup- 

 posed, it really belongs to the family Triarthradae, and the small 

 malleo-ramate jaws (Fig. 3) and two frontal eyes quit' 1 agree 

 with this. 



The two unequal anterior spines spring from the right and 

 left shoulder and lie close against the body when the animal is 

 swimming, so that its mode of progression through the water i- 

 the same as that of Triarthra loityiseta, swimming with its ciliary 

 wreath and ' ; skipping "' from time to time when alarmed. In 

 reality there is no skipping, in the sense of moving forward, as 

 in Polyarthra. The bases of the frontal spines are broadened, 

 and when the head of the animal is retracted the spines stand 

 out straight in front and appear to be quite continuous with the 

 integument, showing no sign of being capable of bending down 

 (Plate 34, Fig. 2). The right anterior spine is considerably 

 longer than the left spine. Posteriorly the spines are terminal 

 and originate close together dorso-ventrally (not side by side 



* Journ. R. M. 8., 1906, pp. 3«»3— 11 J. 



