454 Dr. G. C. Wallich on the Distinctive Characters, Habits, 



initial character. The sarcoblast and mulberry-mass alike have 

 no capsular investiture^ but are supported by the layer of ecto- 

 sarc into which the surface of the protoplasm is differentiated. 

 But, prior to the first stage of development about to be described, 

 aracebasis does not take place ; that is to say, the outer layer is 

 consolidated by mere contact with the medium around, but the 

 reciprocal interchange between it and the endosarc has not as 

 yet received its first impulse. This impulse consists in the evo- 

 lution of one or more contractile vesicles, which make their 

 appearance in the interior, but whether at any definite point 

 I am unable to determine. At first extremely minute, the con- 

 tractile vesicles gradually increase in size, causing the entire 

 body to enlarge materially, but without as yet impairing its 

 perfectly globular figure (PI. VIII. figs. 1 to 3, 6 & 7). In 

 some cases two or even three of these vesicles appear ; but, as 

 the increase in the protoplasmic substance is uninfluenced by 

 that of the vesicles, it frequently happens that the latter con- 

 stitute as much as four-fifths or five-sixths of the contents of 

 the spherule. It is during this distention that the minute nu- 

 cleus, previously absent or obscured by the closely compacted 

 nature of the granules in the sarcoblast or mulberry-mass, may 

 be seen. Of course, up to this point the young Amceba is mo- 

 tionless, and without the faintest trace of internal circulation, 

 except in so far as the gradual distention of the contractile 

 vesicles causes the granules of the protoplasm to shift their 

 positions. In short, the organism consists essentially of a qui- 

 escent spherical globule of sarcode containing granules, a con- 

 tractile vesicle, and a nucleus. 



The second and most important stage now commences. The 

 tension to which the ectosarc is subjected by the endosraotic en- 

 largement of the contractile vesicle, causes it to yield at a certain 

 point ; the spherical outline is at once destroyed by the projecting 

 portion of the vesicle (PI. VIII. fig. 4). The latter bursts, for 

 the first time, through the ectosare, leaving behind a minute mam- 

 milliform projection which constitutes the first rudiment of the 

 villous appendage*. Should more than one contractile vesicle be 

 present, it is invariably urged, by the contractile effort now made, 

 towards the same point to discharge itself; and from this time 

 the discharge occurs only in this region. But polymorphism 

 has now set in. The little machine has been put in motion, 



* In the ' Annals' for June (Plate X. fig. 8), I figured a minute spherical 

 Amceba — one of the few I had then seen, and regarded by me as a " gem- 

 mule." I had not witnessed the detachment of these from the parent 

 mass. This specimen exhibits a " mammilliform process " at one portion 

 of its periphery, which was evidently the site of discharge of the contrac- 

 tile vesicle, although not recognized by me as being of this nature. 



