RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 109 



but the contents had not assumed a globular figure, but had 

 become condensed in the " top " of the shell, and enclosed 

 by a wall on the upper side adapted to the figure of its 

 interior, and in the lower of equal convex figure, so that 

 on the whole the " spore " (so to call it) had acquired the 

 figure of a thick doubly convex lens. (See Plate VIII, 



fig- ^•) . . 



As originally described by Claparede and Lachmann, the 



test was said to form a simple disc, capable, however, of 

 altering its figure and becoming folded ; thus, according to 

 them, the concave or lower side of the test was wholly open. 

 Seeing the capacity for folding and unfolding, as well as 

 the retraction and projection of the hyaline and delicate 

 '^ lower " (oral) wall of the test, it is possible that a 

 form which I have met with may but represent a phase 

 of the same species. But whilst the test of the latter 

 ■when empty and dead seems always to present a deep watch- 

 glass -like figure (that is, when viewed laterally or from the 

 edge, forming externally a broadly and equably rounded 

 arch), the present, in the same condition (viewed also late- 

 rally), presents a figure not unlike that of a very shallow hat 

 with a narrow rim, or that of a round " baking-dish " — 

 the upper contour only gently convex, then suddenly de- 

 pressed and again somewhat suddenly widening out to 

 form the rim. The former, when viewed dorsally, shows 

 the disc more or less gradually fading oif in colour 

 towards the periphery, or if the transition from coloured to 

 hyaline be rather sudden, it is irregular, whilst in the latter 

 the transition is always abrupt and sharply limited, and 

 circular in contour. In fact, the colour in the latter is 

 restricted to the elevated portion, the border or rim (of the 

 *'hat" or ''dish") being colourless and hyaline; hence in 

 this " dorsal " view the median portion of the disc is often 

 seen to be encircled by a tolerably sharp ring of higher 

 colour, itself again immediately surrounded by the colour- 

 less rim, which fact is due to the observer seeing through a 

 greater thickness of substance just at the place where the 

 sudden descent of the contour from the slightly convex median 

 disc takes place down to the outer hyaline border. I think 

 this form also seems to be of somewhat smaller dimensions 

 than the other ; greatest diameter, 0"0015", of the median 

 coloured part of the disc (viewed dorsally) O'OOIS". If we 

 may assume that, when the shell becomes abandoned by the 

 living sarcode, and hence no longer acted upon by the loco- 

 motive or other movements of the organism, it then is unre- 

 strictedly free to assume what may be called its normal 



