50 BRITISH FRESHWATER RHIZOPODA. 
~The form of the internal diaphragm, which 18 
situated centrally, leaving an opening on either side, 
distinguishes this species from P. compressa (Carter) 
Cash which has the diaphragm stretching across the 
whole width of the neck of the test, with an orifice 
on one side only; instances occur in which the tests 
of the latter have no obvious external features to 
mark the neck and indicate the form of the dia- 
phragm; in these cases it may be necessary to 
immerse the tests in oil-of-cloves or canada balsam 
to enable the structure of the diaphragm to be clearly 
seen and their identity established. ’o this occasional 
external similarity of the two species the paucity of 
records of P. rhumbleri in the British Isles may be 
due. 
The forin of the test distinguishes it from P. elisa 
which has a similar type of diaphragm. 
Rhumbler’s name of P. compressa, is preoccupied 
by the species so named by Carter in 1864, described 
on p. 62 of Vol. II, and the present name is suggested 
on p. 162 of the same volume. 
Genus 23. CRYPTODIFFLUGIA Penard, 1890. 
Cryptodifiugia Penarp in Mém. Soc. Genéve, XXXI, i, u 
* (1890), p. 168. 
In Vol. Il one species belonging to this genus, 
C. oviformis Penard, is described by Cash; since then 
three other species have been recorded from the 
British Isles. 
All the members of the genus are remarkably shy 
and seldom display their pseudopodia whilst under 
observation. 
The followimg description of the life-cycle in this 
genus from the observations by Prandtl* is given 
_ by Minchint :— _ 
* Prandtl, H., “ Der Entwicklungskreis von Allogromia sp.,’ ‘ Archiv far 
Protistenkunde, IX, p. 1 (1907). i ; 
+ Minchin, E. A., ‘Introd, to the Study of the Protozoa.’ London, 1912. 
