316 
PROFESSOR E. RAY LANKESTER. 
maintain that the tissue of the Leeches, which is regarded as a 
‘Miver, has a very different signification; it ought to be placed 
alongside of the fatty bodies of the Arthropoda. It is formed 
of cells of various sizes and of variable form, round, elongated, 
sometimes drawn out, and fibrous ; in other cases the cells are 
ramified and the prolongations anastomose with one another ; 
frequently they form tubes with hemispherical prominences ; in 
short, they reproduce all the varieties of form which are pre- 
" sented by the cells which compose the fatty body of Arthropods. 
In Hirudo, Hsemopis, and Nephelis, the cell- content is formed 
by a brown granular mass in greater or less abundance. Just 
as the fat body of Arthropods is in connection with the external 
“ membrane of the tracheae, intestines, &c., so also the tissue of 
" the Leeches, which has wrongly passed, up to the present time, 
for the liver, is in connection with the connective-tissue envelope 
“ of the intestine ; it embraces not only the alimentary tract, but 
it also constitutes the brown envelope of the testicular vesicles, 
the tunica adventitia of the vascular trunks, the loose brown en- 
velope of the nervous system, &c. ; in a word, this liver is simply 
a form of connective tissue, which, in the absence of a proper 
perivisceral cavity, fills up all the interstices situated between 
the organs which it invests. Its resemblance to the fat body of 
Arthropods has other facts to support jt. Thus, although the 
brown granules make up the bulk of the cells, yet it may be ob- 
served {HamopiSj for instance) that, among the brown-coloured 
networks, there are other fibres, the cells of which have, as con- 
tents, colourless granules of a fatty nature ; and, what is still 
more striking, is that in Clepsine and Piscicola a well-developed 
fatty tissue occupies the place of these brown networks. Where 
the cells form, by means of their outgrowths, a system of mesh- 
works the cavities are filled by gelatin. Besides observation on 
" fresh specimens,! recommend the following mode of preparation : 
— A leech is thrown into hot water, it is then dried, and fine 
transverse sections are made, which are then soaked in slightly 
acidulated water. It is then clearly seen that the connective 
^Uissue which envelopes all the organs, taking its point of de- 
parture from the integument, and, traversing all the muscles, is 
“ filled, in certain parts and in its cellular elements, by brown 
granules, and, moreover, that the colouring matter is of the 
same nature as that of the integument.’^ 
Thus, it appears that Leydig had arrived at very nearly the 
same conclusion with regard to the relationship of the botry- 
oidal tissue and the brown fibrous tissue as that to which I 
have been led. He had, however, entirely missed the connec- 
tion of both these forms of the vaso-fibrous tissue with the 
