1 98 Introduction to Animal Morphology. 



a hole in the lorica, which may be sculptured, or elongated 

 into horns in front ; eyes none (Noteus), two (Pterodina), 

 or one four-angled nuchal (Brachionus). Arthracanthus has 

 long, pointed, retroverted lorical spines. 4. Perosotrocha — 

 worm-like, with a rudimental trochal disc. Albertia, parasitic 

 in earth-worms, has only a ciliated oral edge. Lindia, also 

 parasitic, is non-ciliated, with two club-like head processes, 

 and a short bifid foot. Apsilus is a non-segmented, thick- 

 skinned form, found on Nymphaea leaves. The young 

 females are ciliated, and with eyes ; the males retain these, 

 but adult females lose them. Balatro is also non-ciliated. 



CHAPTER XXIX. 



CLASS 7. — HIRUDINEA. 



Mostly aquatic, ecto-, rarely endo-parasites,* con- 

 sisting of a chain of homonomous metameres, called 

 zonites, usually ringed on the surface, but the rings are 

 surface markings, 3-5 being on each zonite. A suck- 

 ing disc exists at one or both ends, the hinder one 

 usually large, the anterior small, often spoon-shaped, 

 sometimes shielding the head. Secondary lateral 

 suckers exist on the feet of Branchellion and on the 

 head of Branchiobdella. The cuticle is smooth, rarely 

 warted (Pontobdella), bristled only in Acanthobdella, 

 ciliated in Malacobdella. The dermis is of loose, 

 round, or angular connective cells, often with stel- 

 late or branched pigment cells (Piscicola), and in 

 it are two kinds of unicellular glands, a superficial set 

 pouring out mucus, either universally distributed or 



• Macrobdella, from Valdivia, is the giant of the order, measuring 2-5'. • 



