308 
PROFESSOR E. RAY LANKESTER. 
in which the metamorphosis of the embryonic protoplasmic 
cells, from which all tissues are developed, commence that 
differentiation which leads to the permanent form of the 
tissue which they constitute. The mother-cells of all tissues 
are either entoplastic ” or ectoplastic,” or both-— that is 
to say, the metamorphosis of their protoplasm is either 
essentially one occurring at the surface of the protoplasmic 
corpuscle, or one occurring deeply within its substance, or 
the two processes may go on in connection with the same 
cell.^ As examples of the two classes I may cite fat-cells as 
essentially entoplastic, and the corpuscles of areolar tissue as 
essentially ectoplastic. No doubt both intra-cellular and 
inter-cellular deposits do occur in one and the same tissue, 
but in most tissues it is possible to point to one or other 
mode of deposition, or of metamorphosis, as that which is 
characteristic. Tissues which present both phenomena in a 
nearly equal proportion may be distinguished as endecto- 
plastic.^^ In the group of the connective tissues we find that 
the very same chemical and physiological result may be ob- 
tained by a metamorphosis which is either entoplastic or, on 
the other hand, ectoplastic. Thus hyaline cartilage is essen- 
tially ectoplastic, whether we take the well-known type with 
rounded corpuscles embedded in a matrix, or the more un- 
usual form with arborescent cells found in the cartilages of 
fish and of Cephalopoda. On the other hand, notochordal 
tissue, which is often loosely spoken of as a kind of car- 
tilage,’^ differs profoundly from ectoplastic cartilage in the 
fact that the cell metamorphosis is essentially entoplastic, 
occuring loiihin the area of the original protoplasmic cor- 
puscle, and not in the form of a deposit surrounding and 
embedding the embryonic unit. In that variety of con- 
nective tissue which chemically differs from cartilage in 
yielding a less dense and resistant product of metamorphosis 
than that which is associated with the name of cartilage, we 
find equally the two great morphological varieties of ento- 
plastic and ectoplastic tissue. Fibrous tissue generally is 
ectoplastic — that is to say, the protoplasmic corpuscles re- 
main more or less intact whilst surrounded by the fibrous 
and lamellar masses to which they have peripherally or 
laterally given origin. This is true of ordinary subcutaneous 
areolar tissue, of tendon, of mucous tissue (umbilical cord, 
&c.), and of corneal tissue. At the same time we find 
in various Invertebrate groups (not in the Vertebrata) an 
^ When this is the case the ectoplastic and the entoplastic products of 
metamorphosis arc usually of a different chemical nature and of different 
physical properties. 
