The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-groups of polychaetes. Annelids are considered members of the Lophotrochozoa, a "super-phylum" of protostomes that also includes molluscs, brachiopods, flatworms and nemerteans. 

The basic annelid form consists of multiple segments. Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion. Septa separate the segments of many species, but are poorly defined or absent in others, and Echiura and Sipuncula show no obvious signs of segmentation. In species with well-developed septa, the blood circulates entirely within blood vessels, and the vessels in segments near the front ends of these species are often built up with muscles that act as hearts. The septa of such species also enable them to change the shapes of individual segments, which facilitates movement by peristalsis ("ripples" that pass along the body) or by undulations that improve the effectiveness of the parapodia. In species with incomplete septa or none, the blood circulates through the main body cavity without any kind of pump, and there is a wide range of locomotory techniques – some burrowing species turn their pharynges inside out to drag themselves through the sediment.
What research has changed something substantially?
What has it changed?
Since what year?
What group are Annelids associated with?
Is that a type of protosome?
What kind?
Are annelids described as not being the same on each side?
What modifier is used to describe their symmetry?
What group are leeches a sub-category of ?
What are they a sub-group of ?
Do most books still classify these creatures into five categories?
How many then?
What is used for motion in the creatures?
A single one?
What is responsible for the separation of segments?
Are they present in all of these creatures?
What does the blood circulate within?
What can fulfill the role of the heart?
What is the formal name for ripples?
What sort of classification does the earthworm hold?
Cladistic research
 Cladistic research since 1997 has radically changed this scheme,
the scheme
 Cladistic research since 1997 has radically changed this scheme, 
1997
Cladistic research since 1997 has radically changed this scheme, 
Lophotrochozoa
Annelids are considered members of the Lophotrochozoa,
Yes
Annelids are considered members of the Lophotrochozoa, a "super-phylum" of protostomes
"super-phylum"
Annelids are considered members of the Lophotrochozoa, a "super-phylum" of protostomes
No
The annelids are bilaterally symmetrical,
Bilaterally
The annelids are bilaterally symmetrical
Oligochaetes
viewing leeches as a sub-group of oligochaetes and oligochaetes 
Polychaetes
oligochaetes as a sub-group of polychaetes
No
Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species.
Three
Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species
Parapodia
Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion. 
No
Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion.
Septa
Septa separate the segments of many species,
No
Septa separate the segments of many species, but are poorly defined or absent in others, 
Blood vessels
In species with well-developed septa, the blood circulates entirely within blood vessels,
Muscles
these species are often built up with muscles that act as hearts. 
Peristalsis
 which facilitates movement by peristalsis ("ripples" that pass along the body)
Oligochaetes
oligochaetes (which include earthworms)