CONNECTIVE AND VASIFACTIVE TISSUES OF LEECH. 317 
hsematophorous vessels, the blood-vessels as they are usually 
called. 
In a much more recent work, however, namely, in his excel- 
lent treatise on the anatomy and histology of the Oligochsetous 
wovm, Phreor^ctes menkeamts KxcYliy f. mikrosk. Anatomie,' 
vol. i, 1865), Leydig has touched upon various points in the 
anatomy of other worms illustrative of Phreoryctes. He there 
figures a small piece of the botryoidal tissue of the Leech and 
remarks on its vascular nature, showing that since the publica- 
tion of his ^ Histologic,^ he has ascertained the fact that the cells 
of the botryoidal tissue form the walls of blood-vessels. 
The observations of Leydig which I have above cited relative 
to the continuity and identity of the epidermic pigment, inter- 
muscular and tunic-forming fibres, and botryoidal or so-called 
hepatic tissue, show that he had arrived at the conclusion that 
what I have called the vaso-fibrous tissue is one and the 
same structural element with a variety of modifications, but he 
has not included in its area the hsematophorous vessels, as I have 
found it necessary to do, nor is the very valuable passage which 
I have cited from the ^ Histologic ^ explained by drawings either 
in that work or by those which the author has given in illustra- 
tion of his most admirable papers, published from time to time 
in the ^ Zeitsch. f. wiss. Zoologie.' 
Injection of the vaso~fibrous tissue . — In the course of some 
experiments made by injecting indigo-carmine beneath the in- 
tegument of the Leech in order to observe (if possible) the excre- 
tion of that substance by the nephridal cells, I was struck by 
the fact that in transverse sections of leeches so treated, the in- 
termuscular brown fibres of the vaso-fibrous system were very 
uniformly coloured blue by the indigo-carmine, to the exclusion 
of other parts of the organism. I am not able to say whether 
this was a mechanical injection of the tubular fibres, or whether 
it was rather due to a selective vital action on the part of the 
vaso-fibrous tissue, similar to that noted in Vertebrate areolar 
tissue by Arnold. I am inclined to think that it was not me- 
chanical since the vessels of the ha3matophorus system were not 
injected. This latter fact could, however, be explained on the 
hypothesis that these vessels were already filled with their haemo- 
globinous fluid, whilst the tubular fibres of the brown fibrous 
tissue were in a non-distended but distensible condition. 
