1 2 PROTOPLASM. 



and incapable of change, animate and inanimate, alive and 

 dead, are some of the opposite qualities possessed by 

 different kinds of matter which have nevertheless been 

 called protoplasm. 



A definition of protoplasm, most probably written by 

 the late Professor Henfrey in " Griffith and Henfrey's 

 Micrographic Dictionary," is as follows : " Protoplasm. 

 The name applied by Mohl to the colourless or yellowish, 

 smooth or granular viscid substance, of nitrogenous con- 

 stitution, which constitutes the formative substance in the 

 contents of vegetable cells, in the condition of gelatinous 

 strata, reticulated threads and nuclear aggregations, &c. 

 It is the same substance as that formerly termed by the 

 Germans ' schleim,' which was usually translated in English 

 works by * mucus' or ' mucilage.' " The surface of this 

 mass constituted the " formative protoplasmic layer" which 

 was supposed to take part in the formation of the cellulose 

 wall of the vegetable cell. This was regarded by Von Mohl 

 as a structure of special importance distinct from the 

 cell contents, and it was named by him, in 1844, the 

 " primordial utricle." 



In cases where protoplasm appears as a simple trans- 

 parent homogeneous substance, several layers have been 

 described, and it has been supposed that these different 

 layers are concerned in different operations. This view has 

 been extended to many forms of protoplasm, and the 

 movements which occur have been attributed to the pre- 

 sence of two or more layers differing in density. 



Clear, homogeneous protoplasm, it has been said, under- 

 goes vacuolation, and becomes honeycombed, the spaces 



