16 
CHARLES BADHAM. 
lacuna found in a numbed of Ichthyobdellid leeches, a fact 
of considerable importance when considered in relation to the 
direction of the flow of lymph in the body-cavity. Proceeding 
to a detailed examination there are found the following 
lacunae ; Dorsal, Yentral, Contractile, and the Segmental 
Lacunae. 
I shall follow Oka and Selensky in the use of the term 
“lacuna” in place of “sinus” in dealing with the various 
portions of the coelome, reserving the term “sinus” for the 
blood-space found round the intestine called by Johansson the 
“ intestinal lacuna.” 
The Dorsal Lacuna may be considered in two parts, the- 
testicular and the intestinal portions. It extends from the 
beginning of the testes to the anal region. In the testicular 
region it contains the dorsal blood-vessel (PI. 2, fig. 8, Dt .) ; 
in the intestinal region it surrounds the thick-walled intestine 
and the blood- stream in relation with it. 
Posteriorly the intestinal portion communicates with the 
ventral lacuna in the anal region. In each segment the dorsal 
lacuna communicates by a pair of segmental lacunae with 
similar extensions of the ventral lacuna (PI. 2, fig. 8, 8. 1.). 
The wall of the testicular portion of the dorsal lacuna has a 
thin well-defined membrane with small elongated nuclei, 
which are scarce. Beneath this membrane are a few muscle- 
fibres. 
The musculature is increased where the dorsal blood-vessel 
is fused with the wall of the dorsal lacuna. 
Frequently the dorsal lacuna is divided into two parts by 
the formation of septa placed dorsallv and ventrally to the 
dorsal blood-vessel (PI. 2, fig. 10, Sep. d. Sep.v.). Such 
septa generally begin with the origin of the valves of the 
dorsal vessel, but do not extend to the preceding or succeeding 
valve-origin ; so that at certain places the dorsal blood-vessel 
lies free in the dorsal lacuna. 
The Yentral Lacuna (PI. 2, fig. 8, v.l.) occurs as a 
tube, which varies in size and runs from the anal region to 
the proboscis, ventral to the alimentary canal. Throughout 
