REFERENCES TO THE PLATES. 



The figures have all lieen dra-wn in their proper proportions upon a scale of measurements, which 

 ~are given in diameters, or in fractions of the millemetre. It was intended to make the drawings goner- 

 ally npon the same scale of measurement, but subsequent comparison of the size of the figures with the 

 actual measurements of the specimens indicated wide variation in the scale. 



The lithographs fairly represent the characteristic features of the specimens, though not so well 

 as the original drawings. The soft protoplasmic structure in general is too darkly and definitely out- 

 lined, and often too deeply shaded. 



In regard to the contents of the animals when visible, so far as the more conspicuous objects are 

 concerned, the relative proportions are preserved. In the case of the food, when consisting of definite 

 forms such as diatoms, desmids, etc., while the shapes and proportions have been mostly represented, 

 comparatively little attention was given to accuracy in delineating the details of their structure. 



In those figures in which a pink ball is observed it is intended to represent the appearance of the 

 contractile vesicle, but generally it is colored too deeply. The same is often represented without color. 

 Arrows drawn with many of the figures mostly indicate the direction of movement in the animals. 



When the size of the figures in diameters is not indicated, it is the same as in the preceding figure 

 in which the measurement is given. 



PLATE I. 



Figs. 1-7.— AMCEBA PEOTEUS. 



Fia. 1. An individual as often obser-?ed shortly after being transferred to the field of the micro- 

 scope. At first simply globular or oval, it quickly projects numerous small pseudopods as represented. 

 At the lower part of the figure the discoid nucleus n and the contractile or pulsating vesicle p. v. are seen. 

 200 diameters. From a ditch below Philadelphia. 



Fia. 2. Another individual of the same kind, and found with the former, with globular body and 

 fewer but larger pseudopOds ; a condition usually succeeding that of the previous specimen. 



Fig. 3. An individual of ramose form ; a condition usually succeeding that of the previous one. 

 The nucleus obscured from view. Two contractile vesicles, of which the more constant and larger 

 marked p. v. A posterior process of the body, a, which in contraction assumed a mulberry-like •ppear- 

 . ance. 6, discharge of effete matter. From a large spring, in which grew cress, on Darby Creek, Dela- 

 ware County, Pennsylvania, October, 1874. 



Fig. 4. A ramose individual with the posterior part as a mulberrylike mass, a. 6, discharge of 

 excrement. Ji, two discoid nuclei, p, v., contractile vesicle. The striated yellow bodies, of which one 

 is discharged, are particles of sawdust. From ooze mingled with sawdust obtained in a ditch below 

 Philadelphia. 



Fig. 5. An individual found with the preceding, and observed in the act of capturing an active 

 infusorian, TJrocentrum, through the aijproach and conjunction (c) of a pair of pseudopods. AnotheT re- 

 cently-captured Urocentrum is seen within the body of the Amoeba. Nucleus of unusual breadth, tf, 

 posterior portion of the body in a mammillated condition due to contraction. J, particle of sawdust. 



Fig. 6. An example of the grotesque appearance often assumed by Amceba proteus, the individ- 

 ual being comparable to a caricatured human face. In the succeeding view the apparent pair of horns 

 were withdrawn, and the face expended itself in the prolongation of the nose. Same locality. 



Fig. 7. A large, palmate individual, represented as in movement from right to left. The poste- 

 rior part of the body, wil.h three mulberry-like lobes, of which the intermediate one contains the con- 

 tractile vesicle. The nucleus, though present, was mostly obscured from view. The endosarc appeared 

 to flow within thick walls of ectosarc,- which often seemed to be longitudinally folded. 250 diameters. 

 Woodstown Pond, New Jersey. 



Fig. 8. Probably young of AMCEBA PEOTEUS. Individual of small size ; in the initial globular 

 form 0.03 mm. in diameter. 500 diameters. Lake on Bridger Butte, Wyoming Territory, August 1877. 



Figs. 9, 10. Probably young of AMCEBA VILLOSA. 666 diameters. From a pond on Darby 

 Creek, Delaware County, Pennsylvania, March, 1877. Habitually of clavate shape, the posterior ex- 

 tremity (a) discoid and minutely villous. The interior containing a small nucleus, many crystals, sev- 

 eral small contractile vesicles, and a few green algas. 



