PL AN ASIAN WORMS. 
389 
would include the remarkable animal Sagitta , which is, how- 
ever, a transition form. The Sipunculi (Grephyrea) connect 
Vermes with Echinoderms. The Round- worms (Nematelminthes, 
comprising the parasitic Ascaris, Gordins , and Echinorhynchus) 
and the Flat- worms (Platyelminthes, embracing the Turbellaria, 
Fluke-worms, and Tape-worms) complete the list, unless we 
include the Echinodermata, which are by the latest writers 
regarded as forming a separate sub-kingdom of equal rank with 
Vermes.* It is to the class Platyelminthes, and the order Turbel- 
laria, that the Planarians belong, forming one of the two 
sections into which that order is now divided. Having, from 
the above brief emuneration of the groups forming the sub- 
kingdom of Worms, seen what are the animals which are held 
to be most akin to those we are about to study, we may de- 
scend a step (or rather two steps) lower, and examine the order 
Turbellaria, and then select one or two individuals of the Plana- 
rian section. Before doing so, however, I must draw the reader’s 
* A Tabulae View op the Classes and Oedees op Veemes. 
Class I. 
jj 
n. 
III. 
)} 
IV. 
V 
V. 
Sub-kingdom : Vermes. 
Annulata (Ringed-worms) 
Orders : Polychceta (Marine) 
Oliyochceta (Land and Fresh-water) 
Discophora (Leeches) 
Gephyrea (connected through the Sea-cucumbers to Echino- 
dermata) 
Orders : Sipunculus, 8fC. 
Potifera (connected to Arthropods and Turbellaria) 
Orders : Cephalotricha (Wheel-animals) 
Gastero-tricha (Hairy-backed animals, Chsetonotus) 
Nematelminthes (Round-worms) 
Orders : Nematodes (Thread- worms, Vinegar-eels, &c.) 
Gordiacea (Hair-worms) 
Acanthocephali (Echinorhynchus) 
Platyelminthes (Flat- worms) 
Orders : Turbellaria (Planarians and Nemertians) 
Trematodes (Flukes, King’s Yellow-worms) 
Cestodes (Tape-worms) 
Order: Turbellaria. 
Sect. A. Proctucha (Nemertians) { a P 10 ^ 0S ^ S . 
v J i Without a proboscis 
'With a straight intestine, 
and generally a probos- 
Phynchocos 
Arhynchia li 
Phabdoccela 
„ B. Aprocta (Planarians) With an arborescent in- 
testine, and no probos- 
1 cis, but an expanded 
t frontlet . . . . Dendroccela 
There is a growing opinion amongst zoologists that the majority of the 
Infusoria may be classed among Vermes near the Turbellaria. Might not the 
Gregarinida also be associated with the Helminthes P 
