THE PROPERTIES OF PROTOPLASM. 67 



THE PROPEETIES OF PROTOPLASM.' 



Bt eenst haeckel, 



PBOFESSOE OF ZOOLOGY IN THE UNIVEESITT OF JENA. . 



THE terra protoplasm, from Gr. irpCiTot;^ first, and TrXdafia, form, is 

 applied to the supposed original substance from wliich all living 

 beings are developed, and which is the universal concomitant of every 

 phenomenon of life. All that is comprehended for brevity under the 

 terra life, whether the growth of plants, the flight of birds, or a train 

 of human thought, is thus supposed to be caused by corporeal organs 

 which either themselves consist of protoplasm, or have been developed 

 out of it. Wlierever nutrition and propagation, motion and sensa- 

 tion exist, there is as their material basis this substance designated in 

 a general sense as protoplasm. The proof of it is held to be furnished 

 by the protozoans called moners, the whole completely developed 

 body of which consists solely of protoplasra. They are not only the 

 simplest organisms with which we are acquainted, but also the simplest 

 living beings we can conceive of as capable of existing; and though 

 their entire body is but a single, foi'mless, small lurap of protoplasm, 

 and (each molecule of it being like the other) without any combina- 

 tion of parts, yet they perform all the functions which in their entirety 

 constitute in the most highly-organized animals and plants what is 

 comprehended in the idea of life, namely, sensation and motion, nutri- 

 tion and propagation. By examining these moners we shall gain a 

 clear conception of the nature of protoplasm, and understand the im- 

 poi'tant biological questions connected with the theory. 



Some moners live in fresh water, and others in the sea. They are 

 as a rule invisible to the naked eye, but some are as large as the head 

 of a pin, and may be distinguished without the aid of a microscope. 

 When corapletely at rest a moner commonly assumes the shape of a 

 simple sphere. Either the surface of the body is quite smooth, or 

 numerous exceedingly delicate thi*eads radiate from it in all directions. 

 These threads are not permanent and constant organs of the slime- 

 like body, but perishable continuations of it, which alternately appear 

 and disappear, and may vary every moment in number, size, and forra. 

 For this I'eason they are called false feet or pseudopodia, Neverthe- 

 less, by means of tliese pseudopodia the monex's perform all the func- 

 tions of the higher aniraals, moving them like real feet either to creep, 

 climb, or swim. By raeans of these sticky threads they adhere to 

 foreign bodies as with arms, and by shortening or elongating them 

 they drag their own bodies after them. Each thread, like the whole 

 body, is capable of being contracted, and every portion of it is as 

 sensitive and excitable as the entire form. When any point on the 



' From the forthcoming volume of Appletons' " American Cyclopaedia." 



