SEASONAL CYCLE IN PERCH SPERMARY 689 
cords and bands. The amount and distribution of the elastic 
tissue is important, since, in the absence of muscle fibers and of 
special ejaculatory organs, it must play some part in the expul- 
sion of the spermatozoa. The reduction of the testis to its nor- 
mal small size after its distention must also depend upon the 
elastic tissue. 
The genital arteries and veins passing into the connective- 
tissue core at the anterior end of the testis give off minute 
branches into the testis as they proceed posteriorly. Elongated 
bodies of adipose tissue are also located in the connective-tissue 
core of the testis and send out digitate processes into the septa 
between the lobules. 
The lobules are irregular-shaped spaces with their apices at 
the center of the testis and their broader ends directed toward 
the periphery. The precise shape can be obtained in the form of 
casts by allowing a testis to soften for a time, fixing it in alcohol 
and then tearing it apart. The hardened mass of spermatozoa, 
representing a cast of the lobule, may then be dissected out 
with ease (fig. 2 a, b, and c). The same procedure may be car- 
ried out with success in testes which contain only the early, 
transforming germ cells. The casts of the lobules appear as 
flattened leaves, joined at their apical ends, diverging and branch- 
ing toward the periphery of the testis. As many as five branches 
may be given off from a single central trunk, and these branches 
may again bifurcate before coming into contact with the testis 
wall. Some of the branches end blindly. In the pickerel the 
branches of the tubules at the periphery of the testis are much 
more finely divided and are convoluted, giving the appearance 
of seminiferous tubules (fig. 23). 
4. Discussion of seasonal histological changes and comparison with 
other animal groups 
From the foregoing description it follows that the perch testis 
differs radically from that of the Sauropsida and the mammals. 
The fact, too that the testis undergoes such a complete seasonal 
change places it in a class far removed from the amniotes. It 
JOURNAL OF MORPHOLOGY, VOL. 32, NO. 3 
