1888.] between the Body-canity and the Vascular System. 215 
me than a development of the coelomic spaces, as Bourne has 
one. 
Again, in Hirudo, where the funnels do not open, the blind 
internal end lies in a perinephrostomial sinus, which again possesses 
no characteristics which would justify the assumption that it is 
fundamentally different from other coelomic spaces. 
Before passing on to consider the means of communication of 
the vascular and coelomic spaces, I wish to insert a few remarks 
upon the sacs which are present on the nephridia, which have 
internal open funnels, and in which numerous corpuscles from the 
blood are found. These corpuscles seem to be degenerating, and 
in some cases they appear rather more granular than the normal 
corpuscles in the blood. 
It has occurred to me that we have to do here with a pheno- 
menon similar to that which Durham’ has described in Asterias 
rubens. The amoeboid corpuscles, after devouring some substance 
which it is to the advantage of the organism to excrete instead of 
working their own way to the exterior, are taken up by the open 
funnel of the nephridium, and in the sac they disintegrate and are 
eventually thrown out from the body. In Asteroideae, where there 
are no nephridia, the corpuscles work their way out through the 
body-wall. 
We owe our knowledge of the paths by means of which the 
fluid passes from the blood vessels into the coelom chiefly to 
Lankester and Bourne. Besides the direct communications which 
exist in the Rhyncobdellidae, there is the communication by means 
of the botryoidal tissue which is seen at its best in the Gnatho- 
bdellidae. A fragment of the brown tissue of a Leech shews at 
once the connection of the lumen of the botryoidal tissue with 
that of the thin walled vessels. And my sections through Clepsine 
and Hirudo shew in numerous places the large openings by means 
of which the botryoidal tissue is put into communication with the 
sinuses, sometimes a continuous coagulum being found, lying half 
in one and half in the other system of spaces. 
The same kind of blood is found in both the true vessels and 
the sinuses, except that, as Bourne pomts out, certain large 
corpuscles which occur in the sinuses of Clepsine and Pontobdella 
are not found in the blood vessels, being, as he suggests, too large 
to pass through the communicating channels. 
The contraction of the dorsal vessel in its sinus can be seen 
without difficulty, and I have often watched the ventral vessel 
contract, sending the blood from before backward, whilst the 
current in the sinus surrounding the vessel flowed in the reverse 
1H. HE. Durham, “ The Emigration of Amoeboid Corpuscles in the Starfish,” 
Proc. Roy. Soc. Vol. 43, p. 327, 
