DEVELOPMENT OF ASCIDIANS. 
395 
(Fig: 188, A, h); whether the primitive opening (Fig. 386‘, 
A, a) is closed or not, Kowalevsky says is an interesting 
question. 
it probably closes. 
The larva hatches in from 
forty-eight to sixty hours af- 
ter the beginning of segmen- 
tation, and is then of the 
form indicated by Fig. 386° 
(copied with some additions 
and omissions from Kupffer’s 
figure, being partly diagram- 
matic). This anatomist dis- 
covered in the larva of As- 
cidia canina, which is more 
transparent than Kowalev- 
sky’s Phallusia larva, not 
only a central nervous cord 
overlying the chorda dorsalis 
and extending well into the 
tail, while in the body of the 
larva it becomes broader, 
clnb-shaped, and surrounds 
the sensitive cavity (a), but 
he also detected three pairs 
of spinal nerves (s) arising at 
regular intervals from the 
spinal cord (A, h’) and dis- 
tributed to the muscles (not 
represented in the figure) of 
the tail; Kupffer calls f the 
middle and g the lower brain- 
ganglion. The pharynx (8), 
or respiratory sac, is now 
very large; it opens pos- 
teriorly into the stomach and 
intestine (4); % represents 
one of the three appendages 
According to analogy with many other animals 
am 
S. 
~. 
Bi on at 
Fig. 3865,—Larval Ascidian. @, sense 
cavity containing the ores ob, pharynx or 
respiratory sac ; ¢, notochord ; ¢, supposed 
auditory organ ; /, middle, g, ‘lower brain- 
ganglion; 2, h, spinal cord; 8, 8, 6, three 
sets of ‘spinal’ nerves; 4, intestine ; t, 
body-wall, consistin of epithelial cella.— 
Copied with some changes from Kupffer. 
by which the larva fastens 
itself to some object when about to change into the adult, 
