! 2 PROTOPLASM. 



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 

 being rilled with watery matter. In some instances, this 

 change proceeds until mere protoplasmic threads are seen 

 stretched across the cavity. The transparent fluid material 

 occupying the spaces and the intervals between the threads 

 supposed to be the less important matter, and yet it is 

 the living, growing, and moving substance ; while the 

 threads and walls of the spaces are composed of matter 

 which has ceased to manifest these properties matter 

 which no longer lives, and which has been formed from the 

 living matter. But we may fairly ask if this lifeless, passive, 

 formed matter, which cannot move or grow or multiply of 

 itself, which is but a product of the death of protoplasm, 

 is nevertheless to be called by the same name as the living, 



