CONNECTIVE AND VASIFACTIVE TISSUES OF LEECH. 309 
entoplastic form corresponding chemically and functionally 
to the ectoplastic forms just cited. This is the grosshlasige 
Bindegewebe the vesicular connective tissue so abundant 
in the Mollusca, in the Nemertines, and other Invertebrata. 
The only tissue which in form represents this among the 
connective tissues of Vertebrata is adipose tissue. Vesicular 
connective tissue stands in the same relation to mucous 
tissue, tendon, and corneal tissue, as does notochordal tissue 
to hyaline or fibrous cartilage. 
Yet further, the tissues of the connective group which are 
specially related to the nutrient fluids (such as blood and 
lymph), and which form the wall of the coelom or of blood- 
channels, may be entoplastic when they give rise by internal 
metamorphosis (liquid vacuolation) to capillary vessels, or 
ectoplastic when they constitute spongy or lacuniferous cell 
aggregates, the cells separated by inter -ce\\\x\?iY channels, such 
as we find in the pulp ” of lymph-glands and the spleen 
and in the lacunar tissue of Molluscs.^ The recognition of 
these two modes of cell metamorphosis appears to me to be 
important, as enabling us to bring together as morphological 
varieties of one and the same tissue, having the same 
chemical and physiological significance tissues, which are 
frequently separated from one another without scientific 
method, or else are abitrarily placed side by side in con- 
sequence of the recognition of chemical and physiological 
resemblances, without sufficient emphasis being given to 
their very different morphological character. 
Ectoplastic and entoplastic connectwe substance of the 
Leech . — In the medicinal Leech two forms, and only two 
chief forms of skeleto-trophic tissue are to be discovered. 
The one is an ectoplastic connective substance resembling 
somewhat the jelly-like tissue of the umbilical cord (PI. 
XXVII, fig. 1) ; this I shall term ectoplastic connective 
jelly ” (in contrast to the entoplastic connective jelly ” so 
abundant in Molluscs). The second kind of skeleto-trophic 
tissue found in the Leech consists of greatly branching and 
anastomosing fibres (PI. XXVII, fig. 1, fb, and fig. 3), 
which are often darkly pigmented by fine granules, and are 
not unfrequently tubular (fig. 4), passing by insensible gra- 
dation and actual continuity of substance into the form of 
very delicate capillaries, which abound in all parts of the 
Leech’s body and contain hsema, that is, fluid impregnated 
with haemoglobin. It is a modification of this tissue which 
forms the pigment patches of the integument (sec PI. 
' Sec 11. It. Peck, “ On the Structure of the Lamcllibraiich Gill,” this 
Journal, 1870. 
