XV REPRODUCTIVE ORGANS 403 
former, or “ gymnoarian,” condition is primitive; the latter, or 
“eystoarian,’ is secondary, and is brought about by the growth 
of two peritoneal folds round the ovary and the union of their 
margins. Into these coelomic sacs the egg-bearing or real ovarian 
tissue projects either in the form of processes or of trans- 
versely- or longitudinally-arranged plates or folds (Fig. 232, B). 
The testes are composed of seminal ampullae, as in Elasmo- 
branchs, or of radially-arranged and sometimes plexiform tubules 
Fic. 232.—Diagrams to show the structure of the testes (A) and of the ovaries (B) 
ina Herring. (From Cunningham. ) 
opening into the gonoduct, as in nearly all other Fishes (Fig. 
Pow, A.). 
In the Cyclostomes (e.g. Petromyzon) the eggs and sperma- 
tozoa are discharged from the gonads into the coelom, whence 
they reach the exterior through a pair of “ genital pores” leading 
from the hinder end of the coelom into a urinogenital sinus 
formed by the united extremities of the two archinephric ducts." 
Myxine has, however, but a single median pore, opening into an 
integumentary cloaca, which also receives the rectal and urinary 
orifices. Ldellostoma has two such pores communicating with 
a similar cloaca.’ 
1 Ewart, Journ. Anat. and Phys. x. 1876, p. 488. 
2 Burne, Linn. Soc. Journ. Zool. xxvi. 1898, p. 487. 
