52 ZOOLOGICAL EXERCISES, 
amine a portion. They will probably be found to 
contain ova. The two smaller rows are attached 
firmly to the descending portion of the intestine, 
They are probably the male organs, but I have never 
found any spermatozoa in them. 
7. The respiratory sac.—Slit the sac open from the fundus 
to the oral opening, and turn back the upper portion 
to the left. The sac is longitudinally plaited. Notice 
the laciniated tentacles surrounding the oral opening 
and pointing inwards: there are eight of them. Cut 
one off and examine with the inch objective. Notice 
the crimson layer surrounding the interior of both 
the oral and atrial openings. Notice the thick white 
rod-like mass, with a fold on each side, lying longi- 
tudinally on the side opposite to the openings. This 
is the endostyle. Cut out a portion of the sac and 
examine it. Notice the small grating-like bars 
crossing the stigmata, or rectangular spaces. With 
the quarter-inch, notice that these bars are hollow 
tubes, and contain granular corpuscles. The edges of 
all the bars are lined with cilia, which will be seen in 
movement if the dissection has been made in salt 
water. 
8. Nervous system.—Cut down very gently into the 
mantle, between the oral and atrial openings. A 
large oval ganglion of a yellow-ochre colour will be 
readily found. It is difficult to get out. 
NOTE I.—In the third tunic, or peritoneal membrane, there are large 
numbers of irregular branched spicules of carbonate of lime. As this 
membrane lines all the viscera, these spicules will be found apparently 
imbedded in most of the organs. I have not been able to recognise @ 
heart in Boltenia. 
Norse IJ.—Any other simple ascidian will do as well as Boltenia, 
but in them the oral opening will be found to be the one furthest away ~ 
from the place of attachment, and the internal organisation will differ to 
some extent. 
