180 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
organs, which one would expect to be respiratory in function, appear to 
be entirely devoid of blood-vessels, so that it is not likely that these 
organs are respiratory, and perhaps no useful suggestion can be made 
until living examples have been studied in their proper habitat. 
Platyhelminthes. 
Valvular Apparatus in Excretory Organs of Trematodes.* — Herr 
K. Kampmann remarks that little is known as to the valvular apparatus 
of these organs in Trematodes, though a good deal has been discovered 
regarding the same apparatus in Cestodes. He finds in all the Distoma 
that he has examined that the collecting vessels open laterally into the 
terminal vesicle ; this allows of a valvular closure of the orifice. The 
arrangements for closing are of two kinds. In Distomum isostomum 
and D. mentulatum the collecting tubes pass almost at a right angle 
into the vesicle, so that when the terminal vessel contracts they are 
closed by the valves which project into the cavity of the vesicle. In 
D. cirrigerum, D. clavigerum, and D. endolobum, the collecting vessels 
form an acute angle with the wall of the terminal vesicle and the wall 
of the tube, which is turned towards the vesicle, fuses with this wall to 
form a membrane, which is thicker at the base and thinner near the 
orifice of the tube ; this membrane, on the contraction of the terminal 
vesicle, is forced by the pressure of the contents in front of the mouth, 
and closes it. 
Ectoparasitic Trematodes of Japan.j — Mr. Seitaro Goto has an 
elaborate memoir on these worms. He commences with an account of 
their anatomy and histology, gives some biological notes on these 
parasites, and concludes with a systematic account of 32 species. Dis- 
cussing the nature of the primitive retractile fibres which constitute 
the wall of the suckers in many genera, he urges that the indirect 
evidence is strongly in favour of the non-contractile nature of these 
fibres. He points out their differences from the ordinary muscular fibres 
of the body and from those of the suckers of various forms. If the 
suckers are non-contractile, the question arises how the suctorial action 
is to be explained. He regards the suckers as forming a bag with a 
thick elastic wall which constantly tends to be flattened out, but which 
is kept in proper shape by an external force, that of the muscular fibres 
that are attached to the bottom of the suckers. If these muscular fibres 
relax, the wall of the sucker becomes flattened out by virtue of its 
elasticity, and applied to its substratum — the body surface of the host. 
If the muscular fibres now contract, the sucker assumes the form of a 
bag, and thus a vacuum tends to be formed within which gives rise to 
suctorial action. 
The penis seems to be most complete in structure in Tristomum and 
Epibdella. In these it is a hollow club-shaped organ, projecting by its 
distal portion into the genital atrium, with which its internal cavity is 
directly continuous, and it is provided with muscular fibres of its own. 
The connective tissue and chitinous penis of Monocotyle seem to the 
author to afford a starting point for another type of copulatory organ, 
* Rev. Suisse Zool., ii. (1894) pp. 443-62 (2 pis.). 
f Journ. Coll. Sci. Imp. Univ. Japan, viii. (1894) pp. 1-273 (27 pis.). 
