146 BRITISH FRESHWATER RHIZOPODA. 



Diameter 8-20 /x ; free embryos 4-8 /x in diameter ; 

 embryos in colonies 2-4 p in diameter. 



Habitat. Submerged vegetation. 



ENGLAND. Sheffield District, W. Yorkshire (Brown). 

 IRELAND. Lough Gatny, Donegal (West) ; Calary 

 and Carrig (Archer) ; Wicklow (Barker). 



The embryos or young individuals are frequently 

 aggregated into colonies which form circular masses 

 about 30-60 //, or more in diameter, from the periphery 

 of which slender pseudopodia radiate. These colonies 

 have amoeboid movements and may divide ; when this 

 takes place the two portions separate until they are 

 connected only by one or two individuals and the very 

 fine elastic filament or filaments, emanating from their 

 apertures, upon which they appear to be threaded like 

 beads. When these break the outlying cells are re- 

 tracted into the portion to which they remain attached. 

 These embryos are about 4 p in diameter and are colour- 

 less and transparent except for one dark spot in each. 



The exact position of D. archeri amongst the Rhizo- 

 poda is doubtful ; it has no affinity with the genus 

 Amphitrema beyond possessing two apertures to the 

 test, but it has affinities with the Reticulosa. It is 

 doubtful if Diploplirys stercorea (Cienk.), found on 

 horse-dung, has any real relationship with D. archeri. 



Penard (' Faune Rhiz. Leman,' 1902) discusses the 

 peculiarities of this species, and his observations may 

 be thus briefly summed up. The plasma never con- 

 tains any food-particles ; the pseudopodia differ from 

 those of other Rhizopoda in that they are stiff and rigid 

 when extended and the animal progresses without any 

 visible movement in them ; the envelope appears to be 

 of a substance resembling that of a vegetable cell 

 rather than that of a Rhizopod ; the oil-like globules 

 enclosed in the plasma, which may be pale blue, yellow, 

 or brownish in colour, and are present even in the em- 

 bryos, recall the characteristics of a chromatophore or 

 of the oil-globules contained in certain plants. 



