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departure from the normal in the number or structure of 
the nephridia. After examining these organs in a 
general way, carefully remove the oblique muscles which 
cover one or two of the nephridia and examine these with 
a lens, noting the various parts. Note the funnel, its 
dorsal lip fringed with processes, its ventral simple lip, the 
excretory portion of the organ, the bladder, the gonad (not 
present on the first nephridium), the blood supply, &e. 
At the breeding season the vesicles may be distended with 
ripe ova or spermatozoa. Remove one of the nephridia 
entire and transfer it, with as little disturbance as pos- 
sible, to a glass slide and examine under the microscope. 
If the worm has been freshly killed the strong action of 
the cilia of the funnel will be well seen. Note the vessels 
of the funnel, some of which have blind dilated endings. 
Note also the gonad traversed by the gonidial vessel. The 
excretory portion of the organ may be cut across; at the 
cut edges the action of the long cilia borne by the cells of 
this portion may be seen. 
VI. Nervous System.—The greater part of the 
ventral nerve cord may be easily seen on pushing the 
alimentary canal to one side. It may be readily traced 
forwards as far as the first diaphragm, but the rest of the 
cord, the connectives, the brain and the otocysts are only 
exposed after the first diaphragm has been carefully cut 
away from the body wall. Very little further dissection 
is required. Tt is often, however, an advantage to cut 
away the pharynx, as sliown in fig. 46. The exposure of 
the brain requires some care. ‘The otocysts are usually 
rather yellowish bodies about the size of a small pin’s 
head, their position is seen in fig. 46. Remove an otocyst 
to a slide, cover it and examine it under the microscope. 
The peculiar quivering motion of the otoliths will be seen 
if the specimen has been only recently killed, 
