Practical Course. 75 
numerous nuclei, but no contractile vacuoles. It reproduces itself by 
simple fission. 
Vorticella is a transparent bell-shaped animacule. It is attached to 
a long stalk, by which it anchors itself. From time to time the students 
will see it draw itself down by coiling up the stalk like a corkscrew and 
then suddenly shooting itself out so as to stretch the stalk straight, 
Round the margin of the bell the students will be able to see a fringe 
of large cilia, which vibrate rapidly. Both the mouth and the anus 
lie in a ciliated groove, which occupies very much the same place as 
the end of the clapper would occupy in a bell. There is a nucleus 
and contractile vacuole, but the students will probably not have time 
to make these out satisfactorily. Vorticel/a reproduces itself both by 
fission, and also by spore-formation preceded by the permanent conju- 
gation of a small free swimming individual with a larger stalked 
one. 
The white blood corpuscle, 
A good example of an ameeboid cell is the white blood corpuscle. 
. Chloroform a frog, extract a drop of its blood and spread it on a slide 
under a cover slip. Examine with the highest power available of 
the microscope. Amongst masses of flat oval yellowish discs, which 
are the red blood corpuscles, the students will be able to muke outa 
few colourless granular cells, which, when carefully watched, can be 
seen to extrude finger-like processes or pseudopodia, 
DISSECTION OF THE EARTH-WORM. ! 
Earth-worms (Lumbricus sp.) are common in damp places about 
Dehra, where they are known as senchwa, The largest available 
specimens should be procured for dissection. They can be readily 
killed either by dropping them into aleohol, or with chloroform. Ex- 
amine a specimen with a lens and make out the following features :— 
(1) The numerous little transverse grooves which divide the 
body into rings or segments. 
(2) The thickened reddish section of the body (cingulum), which 
occupies several segments in the anterior third of the 
length. 
(8) The delicate chitinous membrane (or cuticle) with which the 
whole body is invested. 
(4) The four pairs of short spiues (sete) borne on the ventral 
surface of most of the segments, They can be felt 
on drawing the worm through the fingers. 
1 The common species of earth-worms in India differ markedly from each other in the 
arrangement of their reproductive organs. The following account therefore, which has 
been drawn up from some specimens found near Calcutta in December, will not always 
apply completely in this particular, This is of little importance, however, as the essential 
features of the worm’s structure are thesame in each case. 
