deficiencies in young animals taken out of the brood-pouch of their
mother. (* According to Spence Bate, in Brachyscelus crusculum the fifth
abdominal segment is not amalgamated with the sixth (the tail) but with
the fourth, which I should be inclined to doubt, considering the close
agreement which this species otherwise shows with the two species that I
have investigated.) Even peculiarities in the structure of the limbs, so
far as they are common to both sexes, are usually well-marked in the
newly hatched young, so that the latter generally differ from their
parents only by their stouter form, the smaller number of the antennal
joints and olfactory filaments, and also of the setae and teeth with
which the body or feet are armed, and perhaps by the comparatively
larger size of the secondary flagellum. An exception to this rule is
presented by the Hyperinae which usually live upon Acalephae. In these
the young and adults often have a remarkably different appearance; but
even in these there is no new formation of body-segments and limbs, but
only a gradual transformation of these parts.*

(* In the young of Hyperia galba Spence Bate did not find any of the
abdominal feet, or the last two pairs of thoracic feet, but this very
remarkable statement required confirmation the more because he examined
these minute animals only in the dried state. Subsequently I had the
wished-for opportunity of tracing the development of a Hyperia which is
not uncommon upon Ctenophora, especially Beroe gilva, Eschsch. The
youngest larva from the brood-pouch of the mother already possess THE
WHOLE of the thoracic feet; on the other hand, like Spence Bate, I
cannot find those of the abdomen. At first simple enough, all these feet
soon become converted, like the anterior feet, into richly denticulated
prehensile feet, and indeed of three different forms, the anterior feet
(Figure 44) the two following pairs (Figure 45) and finally the three
last pairs (Figure 46) being similarly constructed and different from