AND SOME NEW OR LITTLE-KNOWN PARASITIC HIRUDINEI. 211 



connected, no doubt, with the water-vascular system, as in Pontobdella. The rich black 

 body, moreover, was ornamented with six rows of white spots (fig. 10). 



The alveoli of tbe caudal disk were disposed in rays rather tban in circles, with 

 radiating muscular bundles between them ; they were circular and cuplike, with a central 

 retractile portion, reminding one of the mechanism of the suckers of the Cephalopoda. 



Attached to the body in a very irregular manner, but chiefly at its fore part, were 

 several of the double tubular spermatophora shown in fig. 9. These curious bodies 

 I have also found on other marine Sinidinei, but always with some characteristic dif- 

 ference. Fig. 6, for example, represents a small black leech with white tubercles, refer- 

 able, apparently, to the genus JPontobdella, found on Rliinobatis in the same seas ; 

 and fig. 7 is its double-barrelled spermatophore, which is quite different from fig. 9 5 

 though obviously of the same nature. Very little is positively known of the generative 

 processes of the marine leeches ; but the facts here mentioned may one day meet with a 

 satisfactory explanation. 



Fig. 13 is a small wbite leech, with two eyes, a retractile proboscis, and, in short, the 

 general anatomy of Glossiplionia, but characterized by possessing seven pairs of ramose 

 lateral branchiae, taking up about the middle third of the body. It was found on the 

 conjunctiva of a green turtle at Huon's Island, on the reef to the northward of New 

 Caledonia. Fig. 14 is another specimen of the same species, but much larger, taken in 

 Shark Bay ; both figures are about double the natural size. Fig. 15 shows one of the 

 branchiae as seen with a power of a quarter of an inch. 



In systems of classification both the Oligochceta and the Ehrudinei come under the 

 head of Abranchiata. But this is evidently a mistake ; for, in the first place, it is difficult 

 to deny the branchial function of the ciliated finger-like organs surrounding the vent 

 in Ok en's genus Prato, of which I have found good examples in the Taro beds of the 

 Fiji Islands ; and, from what has been above advanced, there can be no doubt of the 

 existence of external branchiae in the Hirudmei. 



I have now only to say, by way of apology, that I have written this paper without 

 having the opportunity of consulting any recent researches on the subject ; so that, if I 

 have mentioned things already known to science, they may at least be taken as corro- 

 borative matter. 



DESCRIPTION OF PLATE XXXIV. 



Fig. 1. A little Trematode, with large and complex ventral disk, found in the respiratory siphon of a 

 species of Melo, Shark Bay: a, oral sucker; b, genital opening; c, ventral disk; d, external 

 opening of water-vascular system, x 20 diameters. 



2. Posterior extremity of the disk, with cirri exserted. x 150. 



3. Central portion of the disk, x 300: a, alveoli of the border ; b, intermediate alveoli ; c, openings 



of the cirri. 



4. Small portion of the disk, x 350, to show the cirri in different conditions : a, completely retracted ; 



b, partially exserted, with the apex still inverted ; c, completely protruded. 

 SECOND SERIES. — ZOOLOGY, VOL. I. 2 F 



