PROF. W. A. HASWELL OX AUSTRALASIAN POLYCLADS. 479 



backwards to form the dorsal limb of the vagina. Tlie ootyj)e is characterized by the 

 development of a peculiar spiral ridge of its epithelium. The dorsal limb of the vagina, 

 after receiving on its ventral side the common duct formed by the imion of the lateral 

 uterine ducts, runs backwards as a narrowing tube, which opens behind into tiie median 

 posterior branch of the intestine — a genito-intest'mal passage being thus established. 



The absence of distinct prostate glands, other than the glandular cells in the wall of 

 the antrum, and other features connect this form with Dlscocelis. But in that genus 

 there is a pair of lateral receptacula, and there is a common genital atrium. In Laidlaw's 

 recently -created genus Thalamoplana (i6) there are distinct male and female apertures ; 

 but there is a concentric receptaculum seminis, and the prostatic cells in the epithelium 

 of the antrum are raised on muscular ridges. Illcrocelis, Plehn (i8), is also allied, but 

 has a large receptaculum. The occurrence of the genito-intestinal canal is of such 

 importance that it seems desirable to distinguish the Australian form from the members 

 of these allied genera. 



The discovery of the genito-intestinal canal helps to connect more definitely the 

 receptaculum seminis of Polyciads with parts that occur in other Platodes. The corre- 

 spondence of the canal in question with the similarly-named canal in the Heterocotylea 

 cannot well be doubted ; while the homology between the latter and the Laurer's canal 

 of the Ilalacocotylea, though it may be open to question, seems to have the balance of 

 evidence in its favour *. If we accept this conclusion, we must regard as representing 

 Laurer's canal in the Polyciads not only the genito-intestinal canal of Eaterogonia, but 

 the receptaculum seminis of the Acotylea in general (unpaired in most, paired in 

 Dlscocelis tigriiia, Leptoplana subviridis, and Diplosolenia, with an opening on the 

 dorsal surface in Laidlawia), and the posterior female passage of Ti-igo)ioponis and 

 Tripylocelis. 



Cestoplana atjstralis, n. sp. (Plate 37. fig. 5.) 



I have only obtained a single specimen of a species of Cestoplana, which, superficially 

 at least, is very like the European species C. ruhrocincta, Grube. It is a long and 

 narrow Polyclad, Avhich, as Lang remarks, might readily be taken for a Nemertean ; 

 its length was 2 cm., its breadth 3 mm. The upper surHxce is of a light neutral tint in 

 front, becoming reddish orange further back. Close to each lateral border runs a band 

 of the most vivid vermilion, and a median band of the same runs along the Avhole 

 length. In front the lateral bands bend inwards and unite with one another some little 

 distance from the anterior extremity. Posteriorly the two lateral bands unite just in 

 front of the slight notch or depression at the posterior end, but the median band 

 terminates a short distance in front of this. The narrow space between the latera 

 band and the lateral border is almost colourless. There are very many very minute 

 eyes scattered over the anterior portion, with tlie exception of a zone round the margin. 



The only external difference which I can detect between the Australian and European 

 species is that in the former the three longitudinal bands completely fuse, whereas iu 



• See Goto, 5, p. 154. 



