20 
The Queensland Naturalist. 
July, 1925 
address will be directed mainly tnwai'ds indicatinji- the 
special interest which certain selected examples of our 
fauna possess for the student of distribution, ami at the 
same time to stress the need for more detailed examina- 
tion of our fauna and f]<n‘a, not merely from the ana- 
tomical, but also from the ecological aspect. 
The Oligochaeta. a group of the Annulate worms, in- 
cluding the earthworms and their terrestrial and aquatic 
allies, is very strongly develo}>e(l in Australia. The 
Australian representatives embrace a number of forms 
of great anatomical, systematic and distributional signi- 
ficance. The class Oligochaeta falls into two divisions, - 
known as ihe Mierodrili (Avhich are generally a(|uatic 
and mostly rei^resented by small forms) and ^legadrili 
(which are mainly tei*restrial and include many large 
forms. Whereas tin* Megadrili has lieen faiidy well in- 
vestigated in Australia, Ihe Mierodrili have Ix'eu less 
attentively studied. Naturally the terrestrial forms 
(mainly IMegadrili) have tin* major interest in respect of 
zoogeographical problems, inasmuch as the fresh water 
representatives have greater faeilities for a more uni" 
versal distribution. One family of the Oligochaeta 
known as the Phreodrilidae, has a si)ec*ial interest, in- 
as much as it is restricted to the Southern Hemisphere 
and enjoys a circum])olar distrihution. is strongly repre- 
sented in Australia, and exhibits characters which are 
intermediate between thosi^ of the typical Mierodrili and 
Megadrili. 
Tn the Mierodrili the swollen glandular area, known 
as the clitellum, is a single cell in thickness and is far 
forward in position, whereas in the Megadrili the clitel- 
lum consists of several layers of cells, and is never to be 
found in front of the 12th segment. Tn the Phreodrilidae 
it agrees in structure with that of the Mierodrili, and in 
position with that of the Megadrili. The miniit(^ rods 
known as setae, occurring in each segment of the body 
and serving as levers, are partly in the form of long 
hair-like structures, and partly as sigmoid or S-shaped 
structures, with a bifid or split free extremity in the 
Mierodrili, whereas in the Megadrili they are S-shaped 
with a .simple extremity, Tn the Phreodrilidae the seta*' 
lesemble those of the Mierodrili, but the extremity re- 
calls that of tile Megadrili, the bifid nature being almost 
hidden. There are many anatomical features of the 
Phreodrilidae which recall the Megadrili. or true earth- 
