SCIENCE-GOSSIP. 



2S9 



In the structure of protoplasm, however, many 

 qualities are attained, the attributes of which being 

 invisible are consequently entirely unknown to us, 

 and which undoubtedly determine the course of 

 certain developments. Yet the knowledge we 

 possess of the structural formation of the sub- 

 stance sufficiently demonstrates that living proto- 

 plasm is not merely an organic substance, but that 

 it is an organized aggregation of molecules of 

 organic matter confined into groups and ultimately 

 forming the particles of living matter. The essence 

 of living matter being in a constant state of change, 

 these particles, supposing that at any period of 

 their existence they were alike, would become 

 altered in their state or appearance. Hence it has 

 been questioned whether these particles or micellae 

 are of the same nature, or whether they may not 

 possess different inherent qualities causing changes 

 in the growth of the protoplasmic mass, which 

 may determine the growth in many animals. Con- 

 sequently these units, or micellae, may be regarded 

 as the carriers or germs of any inherited pecu- 

 liarities. Hertwig tell us ( 10 ) that, " with the 

 means of investigation at present at our com- 

 mand, we are unable to discover any fundamental 

 difference between the protoplasm present in 

 animal cells and that in plant cells, or uni- 

 cellular organisms. The uniformity is of necessity 



only apparent for the vital processes 



occur in each organism in a manner peculiar to 

 itself, .... and since the protoplasm is the 

 chief site of the individual vital processes, these 

 differences must be due to differences in the funda- 

 mental substance, that is to say, the protoplasm." 

 Consequently we must accept the theory that 

 protoplasm of different organisms differs in its 

 " material, composition and structure : important 

 differences which are due, apparently, to variations 

 in molecular structure." 



ithstanding the sameness and uniformity in 

 the appearance of the protoplasm, the cell itself, of 

 which the protoplasm forms a more or less im- 

 portant part, when regarded as a whole, may 

 assume a great variation in appearance. This 

 want of uniformity, or irregularity, is partially 

 accounted for by the variations in external struc- 

 ture, but it chiefly arises from the fact that 

 sometimes one substance and sometimes another 

 substance is stored up in the protoplasm in such 

 quantities as to be distinguishable from it, and at 

 limes to much so, that were such bodies to be 

 eliminate] from the protoplasmic mass, their 

 absence would reveal a scries of small vacua. 

 between which the protoplasmic groundwork of 

 the ceil would be visible, having the appearance of 

 a network. This must not be confused with that 

 ■ ■■ structure »t. t lie opinion ■,( 



the protoplasm itself. 



<»J " T»« C«H." Sm«Ii 



Van Beneden has proposed these adventitious 

 elements should be called Deutoplusm, while Para- 

 plasm is the descriptive term suggested for them by 

 Kupffer( n ). Whatever advantages may recommend 

 these descriptive terms, considering that the idea 

 of an albuminous substance is always conveyed by 

 the word "plasm," it has been regarded as safer 

 not to adopt them, but to class these adventitious 

 elements as intraplasmic products and adventitious 

 cell contents. Otherwise to designate them 

 according to their functional attributes, reserve 

 material, and secretions ; or to specify them as 

 yolk granules, fat globules, starch granules, and 

 pigment granules. 



In considering the development of the cell these 

 play important parts, and the difference between 

 these elements and the protoplasm in which they 

 find location is much the same as that existing 

 between the organs of which our bodies are com- 

 posed and those substances which, primarily, are 

 taken up as food by the animal body, to be later 

 on circulated in a liquid form through all organs. 

 The former are termed, on account of being less 

 dependent on the condition of nourishment of the 

 body for the time being, and less subject to 

 the variation, tissue substances, the latter cir- 

 culating substances; in other words, protoplasmic 

 or tissue material, while the adventitious elements 

 are circulatory substances. It will be easier 

 understood from this that the cell is constituted 

 of two parts or divisions : the protoplasmic portion, 

 wherein the adventitious elements, some of which 

 may be unknown to us on account of our inability 

 to differentiate them, find place, and the nuclear 

 section, which of itself contains a nucleus. 



In the Amceba we have a good example of a cell 

 which is constituted of a mass of naked protoplasm ; 

 likewise the Mycetozoa and Reticularia offer very 

 useful media for the study of cell-structure, being 

 unicellular organisms. From their appearance it 

 was supposed these were constituted with a cellular 

 membrane. Taking the Amoeba as an example, 

 we find it a small mass of protoplasm which extends 

 itself into foot-like processes, or pseudopodia; the 

 body is not separated from the surrounding medium 

 by any thin coating or covering, consequently it is 

 termed a naked body ; the only differentiation 

 being, that the superficial layer of the protoplasm 

 ectoplasm which may be regarded as a conden- 

 sation of the hyloplasm, and, consequently, as free 

 from granules — constitutes this exterior zone, 

 thereby giving the appearance of an outer covering) 

 discriminated by the term ectosarc to distinguish 

 it from the darker mass, or indopla.in, whit b il 

 surrounds, called endosarc, and in which the 



I 1 : . "Uebsi <M0i i' lulruna di 1 P plum 1 



or Cewobi li brluan dsi niturwli an- 

 na, fir ScIiIuiwIk-HuIhIcIii. ".I, l„ p, lag. 



IIMl 



