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INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VOL. XXIX, PART I
and in some, even absent. The spermatogonia occur along the lobular wall. They are pro-
minent, measuring 20-28 µ in their average diameter and possess distinct round nuclei. Sper-
matogonia are the only germ cells present during this period (Plate II, Fig. 7). Some of them
have polymorphic nuclei (Plate II, Fig. 7 and 9). The presence of polymorphic nuclei has been
reported in the migratory germ cells of perch [Turner 1919] and Salmo salar [Jones
1940]. However the cord of germ cells outside the testis recorded in the perch [Turner, 1919]
is not present in C. reba.
Stage B : During this stage the spermatogonia with polymorphic nuclei become scarce.
In Ichthyophis glutinosa, Seshachar [1936] observed that the spermatogonia with spherical nuclei
are in an early stage of development and the polymorphic nuclei in these cells denote a con-
dition of great metabolic activity. Further, the transformation of these polymorphic nuclei-
into round ones prior to division is suggested. The rare occurrence of amitosis is also recorded
in Ichthyophis glutinosa. By this auther in C. reba amitosis by nuclear plate formation is obser-
vable in a few spermatogonia (Plate II, Fig. 8). Cysts of primary and secondary spermato-
cytes are present. As in the case of Xiphophorus helleri, [Van Oordt, 1925] and perch, [Turner,
1919] the number of divisions undergone by the spermatogonia to give rise to the spermato-
cytes could not be followed with clarity. The spermatocytes range from 8 to 12 µ in diameter.
The difference between the primary and secondary spermatocytes appears to be only of size,
the secondary spermatocytes being smaller. In some specimens cysts of spermatids are also
encountered.
Stage C : An all round expansion of the testis has resulted in stretching out of the tunica,
and consequently, the latter appears very thin. Stromal elements inside the testis are greatly
reduced and the lobular walls become narrow.
The spermatogonia are remarkably reduced in number and are scattered along the
wall of the lobules which are swollen with cysts of germ cells (Plate II, Fig. 1). The germ
cells of an individual cyst are apparently of the same stage of maturation. The wall of the cysts
is thin and membranous. Elongated nuclei as reported in the homologous cyst wall of Xipho-
phorus hellari [Van Oordt 1925] could not be located in C. reba. During May and June the
cysts of spermatids and sperms are in the increase, and a corresponding decrease of spermato-
cytes and spermatogonia is obvious. The thin cyst wall bursts open in a number of cases to
liberate their sperm contents. When several cysts of an individual lobule break open, the
sperm-filled lumen of the lobule is formed. Sometimes the parachute like arrangement of the
sperms (Plate II, Fig. 3), as reported in perch [Turner 1919] is met with. In a few instances,
connection between the lumina of the neighbouring lobules is formed and the sperm masses
get entry into the vas deferens (Plate II, Fig. 2).
Stage D : The lobules and the vas deferens are filled with sperms. Open connection
between contiguous lobules is extensively present (Plate II, Fig. 4). Secondary sperm ducts
establish connection between the lumina of the lobules and the vas deferens as in the case of
sockeye salmon [Weisel 1943]. Only a few spermatogonia are seen scattered in the lobular
wall. Such germ cells are referred as the 'resting spermatogonia' in Plecoglossus ativelis [Kazuo
suzuki 1939] and residual or persistant spermatogonia in Diemyctylus viridescens [Hargitt
1924]. Cysts of dividing germ cells are negligible.
Stage E : The size variations in the gross structure of the testis denote that the ex-
trusion of sperms takes place in instalments as in the case of ovary. This process is followed
by a steady increase in the number of spermatogonia, which appear along the lobular wall,
a feature in common with Fundulus heteroclitus [Matthews, 1938].
Stage F : The testis is completely spent and resembles Stage A to a large extent.
The tunica once again becomes thick and an enormous increase of stromal elements is evident
(Plate II, Fig. 5). The lumina of the lobules and vas deferens are empty (Plate II, Fig. 6) with
scattered relict sperms in some, which often clump together prior to their disintegration.
A further increase in the number of spermatogonia is noticeable, of which a large percentage
has round nuclei (Plate II, Fig. 5).