600 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
mingled with the sand in the intestine. The vascular system in its 
general relations agrees with that of Echiurus. 
Testes of Leech.* — Prof. A. Schuberg has investigated the minute 
structure of the testes and vas deferens in Hirudo and Aulastomum. 
The conditions in the two genera are almost identical. Particular atten- 
tion is devoted to the testicular epithelium — a single layer of cells which 
exhibits an almost continuous series from typical epithelial elements to- 
cells which closely resemble those of gelatinous connective-tissue. 
Coelom and Vascular System in Leech.f — Mr. E. S. Goodrich has 
endeavoured to ascertain whether in Hirudo medicinalis the cavities of 
the so-called sinus system do or do not communicate with those of the 
contractile vascular system. According to the older interpretations such 
a connection existed, but the recognition of the sinuses as ccelomic made 
their connection with the vascular system seem very improbable. The 
result of Mr. Goodrich’s researches (by injections and by sections) is to 
show that the continuity does exist. 
The injection experiments, in which Mr. L. J. Picton shared, showed 
that both in Aulastoma and in Hirudo blood-vessels, sinuses, and botry- 
oidal tissue are in free communication. The communication takes place 
through the capillary system. 
The baemolymph system of Hirudo consists of four main longitudinal 
trunks, sending out transverse branches to the body- wall. The dorsal 
branches of the lateral vessels pass into small annular vessels communi- 
cating with the plexus of minute capillaries in the epidermis. From 
these, again, arise capillaries going to small sinuses which run into the 
lateral transverse sinuses, and so into the dorsal sinus. 
Similarly the ventral sinus sends annular sinuses along the ventral 
region of the body-wall opening into the epidermal plexus, whence arise 
capillaries joining the latero-abdominal vessels. 
Continuity between the two systems has also been shown to take 
place by means of capillaries on the wall of the alimentary canal, and 
probably exists on the other internal organs of the body. 
The presence of valves, which the author describes, shows that the 
haemolympli must flow in a constant direction. “It seems extremely 
probable that the annular vessels collect the oxygenated blood from the 
epidermal plexus, and carry it into the latero-dorsal and latero-lateral 
vessels, whence it would be pumped into the lateral vessels. From these 
some of the haemolymph must be carried by the latero-abdominal vessels 
to the various organs of the body, and to the ventral cutaneous plexus. 
The annular sinuses would collect it from this plexus, and carry it into 
the ventral sinus. The abdomino-dorsals and the dorsal sinus would 
appear to supply the dorsal and lateral cutaneous plexus.” 
That the lateral vessels belong to the real vascular system, and that 
the ventral sinus and perinephrostomial sinuses belong to the true 
coelomic system, seems certain. Mr. Goodrich is inclined to think that 
the dorsal sinus may represent the dorsal vessel of other Annelids. The 
annular channels may possibly represent the annular coelomic lacunae 
described by Oka in Clejpsine , and it may perhaps be through them that 
* Zeitschr. f. wiss. Zool.. lxvi. (1899) pp. 1-15 (1 pi.), 
f Quart. Journ. Micr. Sci., xlii. (1899) pp. 477-95 (8 pis.). 
