PROTOPLASM AND TIIE CELL. Getl. Sub. 63 
derm and endoderm ; nerves arise in it in situ ; Sedgwick (644). — 
Adequacy of the cell theory : Answer to Sedgwick’s criticism. In many 
cases, as in Nereis and Utiio, the distinctness of the embryonic cells is 
quite clear. Cell-lineage is often demonstrable; a syncytial character 
seems exceptional. Cell -formation, in short, is a very general phenome- 
non in organic life, a characteristic expression of the formative forces 
which reside in organic substance ; Bourne (58). — That organisms have 
a constitution which may be described as cellular is a statement of fact, 
not a theory. Theory comes in when we try to account for the fact. In 
many cases the division of the ovum is not complete. In many cases 
embryonic processes are not marked by the formation of distinct cells. 
Cell-formation is certainly very general, but is it primitive ; or was the 
differentiation of the Metazoa effected in a continuous multinucleated 
plasmatic mass ? In any case, what is the meaning of the predominance 
of the structure called cellular ? Sedgwick (645). 
Definition of cell, as a corpuscle of protoplasm which contains a spe- 
cialized elemont, nuclein ; Bourne (58). — Classification of cells : 
Discrete and independent, c.g., leucocytes ; discrete and coherent, e.g ., 
many blastomeres. Concrescent and conjunct, united by bridges of pro- 
toplasm, e.g., in many tissues ; concrescent and continuous, with proto- 
plasm fused, but nuclei distinct, e.g., plasmodia ; Bourne (58). 
Organic structure : Account of Biitschli’s further demonstration 
of web-like or vacuolar structure in many kinds of organic substance. 
That of cellulose and chitinous membranes may be due to the 
coagulation or precipitation of soluble membrane-making substances; 
Dreyer (157). — Minute structure of red-blood corpuscles; Deiiler 
(142). — Structure of leucocytes; Siedlecki (653). — All cells have a 
protective limiting membrane ; Niessing (491). — All cells agree in being 
readily permeable by solutions of simple alcohols, ether, chloroform, 
simple aldehydes, acetone, and many other compounds ; Overton 
(505). — Protoplasmic continuity of cnidoblasts in Physalia ; Goto (254). 
— Intercellular connections between endothelial cells, and between them 
and the connective tissue between the smooth muscle-fibres ; Nicolas 
(490).— Intercellular bridges ; Flemming (203).— Nature and function of 
iutercellular bridges in epithelium ; Garten (235). — Chromatin has in it 
some assimilated iron compound as a constant constituent ; Macallum 
(4)5). 
Structure of nerve-cells ; Flemming (205). — Present state of know- 
ledge as to the nerve-cell; Nissl (492). — Relation of form of cell (in 
Protozoa) to composition ; Le Dantec (382).— Minute structure of nerve- 
cells in Invertebrates ; Pflucke (524) ; see also Histology, p. 56. 
Fragments of cellular biology ; Kunstler (367). — Cell-studies; 
Niessing (491). — Changes in nerve-cells during activity ; Valenza 
(706). — Study of the pancreatic cell in repose and in activity ; 
Moitret (483). — Physiology of the cell ; Sachs (609). — Localisation 
of respiration in the cell ; Loeb & Hardesty (406). — Slow death 
of cells ; the formation of fat, the progressive destruction of the 
