448 DR. S. F. HARMER ON THE 



(2) Frederi:;ella sultana Blumenbacb. (PI. LXIII. fijjs. 11- 

 14.) 



It is unnecessary for me to discuss the synonymy of this 

 species, since there is a general agreement with regard to it 

 among practically all recent writers. Excellent accounts of the 

 species are given by AUman (56), Kraepelin (87), a,nd many 

 others. It was recorded by Kraepelin (85, p. 6) as one of the 

 commonest forms found in the Hamburg Waterworks system ; 

 and I suspect that one of the species of " Flumatella " recoi-ded 

 by De Vries (90) from the Rotterdam Waterworks may have been 

 really Fredericella. 



I have myself found F. sultana in two English waterworks ; 

 namely the system (No. 4) in which the Pahidicella above described 

 occurred and at Batley. In both cases the material was collected 

 in October, and the polypides had already degenerated, leaving 

 empty tubes containing statoblasts. The tubes show the septa 

 which have been described by Allman (56, p. 112), Kraepelin (87, 

 p. 100), and othex'S, at the point where a tube diverges from the 

 main stem. The statoblasts are developed in both localities with 

 greater profusion than is sometimes the case in this species. 

 Kraepelin has commented (pp. 103, 104) on the variability of the 

 statoblasts of F. sultana. He states that it is hardly possible to 

 find two alike in the same colony ; and that they may be reni- 

 form, almost quadrangular, or even nearly circular. The average 

 length is given by him as 430 /^, and the average breadth as 300 /^(. 

 The length varies between 380 jj. and 570 ^ ; and the breadth 

 between 210 fx and 370 /x. 



Figs. 11-14, taken from the Batley material, show that my 

 own results are in close agreement with Kraepelin's. The varia- 

 tion in form is sufficiently obvious from these figures. The 

 average length of nine statoblasts from Batley was 444 jjl, a 

 measurement almost identical with Kraepelin's. The exti'eme 

 measurements were 416 ^ and 480 yu. The average breadth of 

 the same nine specimens was 242 ^ — somewhat less than Kraepe- 

 lin's figure, — while the extremes were 200 // and 272 //. Some 

 were more than twice as long as broad (fig. 14) ; while the 

 statoblast shown in fig. 11 is almost circular. 



Kraepelin states that the funiculus of Frede^-icella generally 

 gives rise to one or two statoblasts, rarely to three. In my own 

 material, while many of the zooecia contain a single statoblast, 

 and others contain either two or three, one of the tubes in the 

 Batley material contains four statoblasts, which certainly belonged 

 to one polypide. In several instances it can be seen that the 

 statoblasts are closely adherent to one wall of the tube. In cases 

 where two tubes are connate, the statoblasts are adherent to the 

 common wall which separates the two tubes. In the Batley 

 material the statoblasts are almost black in colour, and a large 

 proportion of them, although still contained in the zooecia, have 

 split into their two valves, between which can be seen a mass of 

 living tissue. This is a clear sign that the statoblasts are ready 



