GASTEROPODES. 275 
pointed by Nature for introducing the young of animals to existence, 
affording a noble field of observation to the speculative philosopher. 
A singular variety prevails among the different species of the tribe 
wherewith we are now engaged—one of the most prolific inhabiting the 
waters of the deep. 
Probably the Zritonia Hombergii begins to breed at an early age, 
and continues fertile very long. The presence of an ovarium and its 
gradual advances, may be detected in many specimens through the 
transparent skin of the under surface. 
Having attained maturity, the spawn is discharged as a rope from 
the oviduct on the right side of the body. The parent affixes the end of 
the rope to the solid substance whereon it rests, and gradually withdraws 
during its further discharge. But its course being around the point of 
fixture, the rope escaping forms a regular logarithmic curve, which, 
from a peculiarity, is waved throughout the whole length. 
The spawn of smaller specimens is commonly of beautiful regularity, 
consisting of four or six waving coils or volutes. 
But mark the provisions of Nature. In delivering itself of its pro- 
geny, the parent must quit the original spot of fixture. If it did not re- 
treat a mass of spawn would remain, but to preserve the whole entire 
and undisturbed by its body, the second coil is apart from the first, and 
the third from the second, hence an elegant figure from this mute mathe- 
matician. 
Such is the result when the specimen is quite free and open ; and 
sometimes a perfect form is produced. But such an extensive surface as 
a larger specimen would require being generally interrupted or irregular, 
corresponding irregularities disfigure the arrangement of the spawn.— 
Plate XX XIX. fig. 1. 
Thus the arrangement of the spawn from smaller specimens is more 
definite. From whatever specimen it issues, however, the arrangement 
peculiar to the species may be discovered. Nor does this belong exclu- 
sively to Homberg’s Doris, for, as we shall see, it extends to others. 
The ovarium of the present species is very ample. Its progress is 
exposed through the skin of the under surface, and from fainter indica- 
