466 Dr. G. C. Wallich on the Distinctive Character's, Habits, 



Postscript. 



The experiment about to be recorded was brought to a close 

 after the preceding pages were sent to press. 



On the 27th of last month, a small quantity of the confervoid 

 material, which had previously been kept in water for several 

 weeks, and contained living Amcebce in abundance, was placed on 

 a plate of glass, covered by a bell-glass, and permitted to dry 

 within doors by evaporation. On the 29th ult. all trace of 

 moisture had vanished, the mass forming a dark-coloured har- 

 dened film, which it was difficult to remove. On the 18th of 

 the present month — that is to say, after having been subject to 

 complete desiccation for twenty- one days — the plate of glass 

 was placed in a saucer and covered to the depth of half an inch 

 with distilled water. It remained in this till last evening, when, 

 on examination under the microscope, the confervoid substance 

 was found to contain numerous minute Amceha ]\x%t evolved from 

 sarcoblasts and becoming polymorphous. All the mature forms 

 were killed, not only of Amoeba, but of the Nitzschia associated 

 with them. On the other hand, the sarcoblasts were nume- 

 rous. Hence the fact, that the latter are able to undergo 

 perfect and long- continued desiccation without destruction of 

 their vitahty, is conclusively established. 



EXPLANATION OF PLATE VIIL 



The letters c and n respectively denote the contractile vesicle and nucleus in 

 all the figures in which these organs are present. 



Figs. 1 to 5 represent successive stages in the development of the young 

 Amoeba from a free sarcoblast. 



Fig. I. First stage, which dates from the evolution of the contractile vesi- 

 cle c. The nucleus, if present at this period, is wholly obscured 

 within the granular sarcoblast. 



Fig. 2. Second stage, in which the sarcoblast has become considerably en- 

 larged, chiefly through the dilation of the contractile vesicle, c. 

 The nucleus, n, is now distinctly visible. Diameter of sarcoblast 

 about xiVo tb of an inch ; of nuclear mass about g-o^grth of an 

 inch. 



Fig. 3. Sarcoblast further enlarged, a second contractile vesicle, c", add- 

 ing greatly to its distention. 



Fig. 4. Third stage. This marks the transition from the sarcoblast to the 

 Amoeban form. The spherical outline is now lost, omng to in- 

 ordinate distention ; and the primary contractile vesicle, c, per- 

 forms its discharge for the first time. 



Fig. 6. Fourth stage. Polymorphism has now commenced, and the villous 

 appendage becomes rapidly formed by the repeated discharges of 

 the contractile vesicles. Longest diameter of specimen about 

 Tj-|-o th of an inch. 



Fig, 6. The first stage in the development of the young Amaba from a free 

 acapsular nucleus ; contractile vesicle, c, just showing itself as 

 in tig. 1 . Diameter of mass toVo th of an inch. No nuclear body 



