72 Introduction to A ni/u a I Morphology. 



moniliform pulsating vesicle. 14. Stentoridae — funnel-shaped, 

 naked (Stentor), or surrounded by a gelatinous capsule, with 

 a spiral peristome of long cilia, mouth and anus close in the 

 same groove ; nucleus moniliform ; front of the body two- 

 valved (Freia) or ribbon-like, spirally inrolled (Chaetospira). 



Sub-order 4. Hypotricha — only ciliated on one (the 

 under) side ; including four families. 15. Oxytrichidse — pos- 

 sessing bristles (Oxytricha, Fig. 8, A), hooks (Kerona), or styles 

 (Urostyla), or both hooks and styles (Stylonychia), by help of 

 which they can walk ; shell-less, or with very thin test and 

 marginal cilia ; one form (Kerona polyporum) is parasitic in 

 Hydra. 16. Euplotidse — with a distinct test, hooks and 

 styles, ex. Euplotes. 17. Dysteridae — with a tail-like foot, 

 and a membranous carapace of two separate (Iduna), or united 

 valves (Dysteria), or with no carapace (Huxleya). 18. Aspi- 

 discidae — shield-shaped, with a test ; cilia reaching to the 

 anterior edge ; pharynx not obvious ; locomotory process as in 

 Euplotidae, but with no fine cilia. 



CHAPTER XI. 



SUB-KINGDOM II. — POLYSTOMATA [Huxky). 



Aquatic animals, made up of differentiated plastides, 

 bounding a central cavity, thus forming Gastrulse. 

 The cavity communicates with the external water by 

 many pores or interstices between the cells of the wall, 

 as well as by one or more terminal mouths or oscula 

 formed by absorption at one point in the wall of the 

 polyplast [Haeckcl), or by invagination (in Sycon 

 ciliatum, Mctschnikoff). Sexual reproduction often 

 occurs, but there are no highly specialized tissues. 



There is one class included : — 



Class i. Porifera {Grant) — Sponges, whose 

 characters are those of the sub-kingdom. 



