Iv REPRODUCTION 129 
dorsal hollow outgrowth from the brain. In the young animal 
the olfactory pit opens by the neuropore into the central canal 
(Fig. 80, A), but that passage is closed in the adult. Possibly 
the olfactory pit is homologous with the hypophysis or pituitary 
body of Vertebrates, the homologue of which in Tunicata has a 
ciliated funnel. Finally, the median cere- 
bral eye (Figs. 80 and 81) is a mere pigment 
spot in the anterior wall of the cerebral 
vesicle, and a series of somewhat similar 
pigment spots occurs along the floor of the 
central canal in the spinal cord.’ There is 
no known auditory organ. On the under 
surface of the oral hood patches of cilated 
epithehum drawn out into rounded lobes c 
Y 
were called by Johannes Miiller the “ Rader- 
organ.” This is probably of use in drawing 
water inwards to the pharynx, but it may 
also be a sense-organ. 
The Gonads are segmentally arranged 
along the sides of the body, projecting into 
the atrial cavity at the sides of the pharynx => 
and intestine. In some species the gonads 
are paired, but in others belonging to the 
genus Asymmetron (p. 137) only a single G3 
series, that of the right side, is present. In S 
the common hoppers (Branchiostoma Re 
lanceolatum) there are about 26 pairs (Fig. 70, 
B), lying in somites 25 to 51; and ovaries Fic. 81.— Branchiostoma 
; pac , : ieee $ lanceolatum. Anterior 
and testes are found in separate individuals peeion oceans 
in all other respects. Each gonad is sur- ous system from above, 
. led b lav f lomi ‘theli showing dorsal and 
rounded by a layer of coelomic epithelium. Saini aime AGLT EE. 
The gonad must therefore be regarded as hav- (From Willey, after 
z ; Schneider. 
ing grown down from a myotome of the body- 
wall into a coelomic pouch, carrying before it the coelomic and 
then the atrial epithelium (Figs. 72, and 74, A,g). Eventually the 
gonads, when ripe, burst through the layers of epithelium, and 
the ova and sperms are shed into the atrium and escape to the 
exterior by the atriopore, or it may be in some cases by the mouth. 
1 The cerebral eye and the pigment spots of the spinal cord are especially 
prominent in the oceanic species Branchiostoma pelagicum, Giinther. 
VOL. VII K 
