64 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
REPRODUCTIVE ORGANS. 
Ascidians are not divided into two sexes, and conse- 
quently each individual is hermaphrodite, or possesses both 
male and female reproductive organs (gonads), although 
cross - fertilization is probably the rule as a protogynous 
condition is very general—the female organs maturing 
before the male. In Ascidia mentula, however, self- 
fertilization does sometimes take place. The gonads in 
Ascidia le close together on the left side of the body, 
alongside the stomach and intestine (PI. IL., fig. 4, gon.), 
and are provided with delicate ducts (gd.), which open like 
the intestine into the atrium; so that the mature ova and 
spermatozoa are carried out of the Ascidian’s body by the 
current of water flowing from the atrial aperture. In 
many Ascidians fertilisation and development take place 
in the atrium, a part of which may be set aside as an 
incubatory pouch. In some Ascidians (certain Moleulide 
and Cynthude) reproductive organs are present on both 
sides of the body, and in others (Polycarpa) there are 
inany complete sets of both male and female systems 
attached to the inner surface of the body-wall, on both 
sides, and projecting into the peribranchial cavity. 
The ovary in Ascidia mentula is a slightly ramified gland 
which occupies the greater part of the intestinal loop (PI. . 
II., fig. 4, gon.). It contains a cavity which, along with 
the cavities of the testis, is derived from an embryonic 
mesodermal space which has been compared with a ccelom 
but may be merely blastocoelic, and the ova are formed on 
its walls and fall when mature into this cavity. The 
oviduct is directly continuous with the cavity of the ovary, 
and leads forward alongside the rectum, and external to 
the vas deferens to open into the atrium. 
The testis is composed of a great number of delicate 
branched white tubules, which ramify over the much 
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