Practical Course. 89 
the connecting membranes, and make out tbe following parts. They 
are very complicated, and the students will not be expected to have more 
than a general idea of their structure :— 
(1) The small irregular glandular body (hermaphrodite gland) which 
is embedded in the upper coils of the liver. In this 
the ova and the spermatozoa are alike said to. be developed. 
(2) A slender, much convoluted duct (hermaphrodite duct), 
which connects the hermaphrodite gland with the expand- 
ed portion below. 
(3) The large, firm, white albumen gland, which lies at the side 
where the hermaphrodite duct terminates. 
(4) The large common duct, which is imperfectly divided longi- 
tudinally into two passages, one for the ova and the other 
for the spermatozoa. Sometimes one side of the common 
duct will be found to be crammed with yellowish-white eggs. 
(5) Beyond the common duct, the yassages for tle exit of the 
ova and spermatozoa separate into an oviduct and vas de- 
ferens respectively. Follow these down to the common open- 
ing, noticing the long sac-like branch of the oviduct (recep- 
taculum seminis) in which the spermatozoa received from 
another individual are stored. 
Notice the large columella (retractor) muscle, which sends branches to 
the tentacles, mouth, reproductive organs, etc. It is attached, as we 
have seen, to the shell, and serves to retract the various organs. 
Dissect away the fibrous tissue which composes the outer pait of the 
broad collar which surrounds the cesophagus, and make out the pair of 
yellowish-white nerve masses (supra-cesophageal ganglia) which it con- 
tains. Trace the two nerves which pass down on either side from the 
supra-cesophageal ganglia, to join the large nerve mass (sub-cesophageal 
ganglia) which lies below, thus constituting a complete ring round the 
gullet. The large nerve masses above and below the gullet give off 
nerves which supply the sense organs and other parts of the body. In the 
substance of the sub-cesophageal nerve mass is imbedded a pair of small 
auditory orgaus which are connected by slender nerves with the supra- 
cesophageal ganglia. 
Slit open the mouth and extract the toothed tongue-like organ 
(odontophore) which occupies a large sac in the lower part of the mouth, 
Examine it with your lens and make out the teeth. 
DISSECTION OF THE MAHSEER. ? 
The Mahseer (Barbus tor), which is exceedingly common in the 
streams about Dehra, may conveniently be taken to illustrate the more 
1 It may be necessary to curtail or omit this dissection for want of time. 
