DACTYLOSPH^RIUM RADIOS UM. 67 



Dimensions variable : diameter of body usually about 

 30 ^; length of pseudopodia sometimes 120^u, or over. 



In marshes and pools, amongst submerged vegeta- 

 tion, and in moss on dripping rocks ; less common than 

 Amoeba proteus, with which it is often associated. 



The rayed disposition of the pseudopodia and their 

 rigid habit are characteristic of this species. Fre- 

 quently the arms are curved, bent at an angle, or 

 waved. A pseudopodium in extending or retracting 

 will sometimes assume a spiral form and remain rigid 

 in that attitude indefinitely. The endoplasm, as a 

 rule, is uniformly granular, and the chlorophyllous 

 matter occupying it is sparser than in the common 

 AmoebsR. 



Biitschli transferred this form to the genus Dach/Jo- 

 spliserium (which he named in error Dactylosphaeria), 

 though it must be confessed that there are few points 

 of affinity between it and D. poll/podium, so that there 

 is some ground for Vejdovsky's view that it should 

 form the type of a new genus which he named 

 Astramceba. Penard, however (' Faune Khiz. du Bass. 

 du Leman '), does not consider that either Dactylosplife- 

 rium radio-sum or D. poly podium should be separated 

 from the true 



2. Dactylosphaerium polypodium (Max Sch.) Biitschli. 

 (Plate III, fig. 12; PI. IV, fig. 12.) 



Amoeba polypodia MAX SCHULTZE Organism. Poly thai. (1854), 

 t. viii, f. 21 ; F. E. SCHULZE in Arch. f. mikr. Anat. XI 

 (1875), p. 592, t. xxxvi; ALLMAN in Journ. Linn. Soc., 

 Zool. XIII (1877), p. 276; GLAUS Lehrb. Zool. (1885), 

 ff. 11, 134, and (Engl. transl.) Text-book Zool. I (1884^, 

 p. 22, ff. 11, 121; GrRPBEE in Zeits. f. wiss. Zool. XI 

 (1884), p. 128; MAGGI in Rend. R. 1st. Lomb. (2) XXI 

 (1888), p. 306; HERTWIG Lehrb. Zool. I (1891), p. 149, 

 f. 116; ed. 2 (1900), p. 160, f. 114; and (Eng. transl.) 

 Man. Zool. (1903), p. 189, f. 119; SEDGWICK Text-book 

 Zool. I (1898), p. 4, f. 2; JORDAN & KELLOG Anim. Life 

 (1900), p. 8, f. 4 ; CALKINS Prot. (1901), p. 80. 



