8o PKOCEEDINQS OF THi: 



study of protoplasm, this line of investigation being understood in 

 its widest sense :is the study of the living substance and its vital 

 powers and manifestations, ytrictly speaking, such investigations 

 are co-extensive witli the whole range of the biological sciences, 

 but for convenience the study of ])rotoplasm may be regarded as 

 the special theme of that branch of scientific investigation 

 which is occupied with cells and with organisms of simple struc- 

 ture, and which deals with their constitution, development, and 

 elementary vital activities. In such objects we are confronted 

 with the stupendous mystery of life under its thinnest veil, and 

 we observe in bodies almost infinitely minute the exercise of the 

 most extraordinary powers, such as would lead us to infer the 

 existence of a very great complexity of organization. Thus a 

 flagellum performs movements which necessitate the assumption 

 of a complex structure, but after studying it with the best optical 

 instruments and the most refined technique, we can only repre- 

 sent it by a bare pencil-line. The chroraatin-substance of the 

 nucleus exhibits marvellous activities and powers, but again our 

 pencils can only draw meaningless dots. Xothing, again, is more 

 wonderful than the fact that peculiarities in the complex mental 

 and physical constitution of a human being should be transmitted 

 from one generation to another through the nucleus of the sperma- 

 tozoa, the tiniest cell in the body ; but with all the technique at 

 our disposal we can only represent that nucleus as a minute dense 

 refringent body, apparently homogeneous. A consideration of 

 such facts forces upon us the conviction that the living substance 

 possesses a complexity of organization far transcending anything 

 that our microscopes can reveal, and only to be inferred from the 

 activities manifested by it. 



Cells or unicellular organisms relatively higher in the scale 

 possess various cell-organs for the exercise of different functions : 

 but as we descend the scale in our survey of nature we see these 

 organs stripped off, as it were, until we come to cells in which the 

 living substance consists only of two parts, termed respectively 

 the cytoplasm and the nucleus. .This type of structure is far, 

 however, from being the simplest possible condition of a living 

 organism. The cell-nucleus itself is essentially a collection of 

 grains of a peculiar substance known as chromatin, which is com- 

 bined with various accessory structures, such as a framework,^ 

 membrane, &c., and organized into a complex structural unit. In 

 the simplest organisms there is no definite nucleus, in the strict 

 sense of the word, but only scattered grains of the chromatin- 

 substance. Hence the living substance, protoplasm, in its simplest 

 form consists of two chief constituent parts : — 



(1) Cytoplasm, a semi-fluid matrix, itself organized and ex- 

 hibiting a minute structure which, according to the alveolar theory 

 of Biitschli, is due to the arrangement of at least two distinct 

 substances not miscible one with the other, forming the alveolar 

 framework (reticulum) and the enchylema (cell-sap) respectively. 



