work, confirmed Goodsir's statements in 1846, and, as above mentioned,
took out of the brood-pouch embryos advanced in development and
resembling their parents. By this the question whether the Diastylidae
are full-grown animals or larvae, is completely and for ever set at
rest, and only the famous names of Agassiz, Dana and Milne-Edwards, who
would recently reduce them again to larvae (see Van Beneden, 'Rech. sur
la Fauna littor. de Belgique' Crustacees pages 73 and 74), induce me, on
the basis of numerous investigations of my own, to declare in Van
Beneden's words; "Parmi toutes les formes embryonnaires de podophthalmes
ou d'edriophthalmes que nous avons observees sur nos cotes, nous n'en
avons pas vu une seule qui eut meme la moindre resemblance avec un Cuma
quelconque." The ONLY THING that suits the larvae of Hippolyte, Palaemon
and Alpheus, in the family character of the Cumacea as given by Kroyer
which occupies three pages (Kroyer, 'Naturh. Tidsskrift, Ny Raekke,' Bd.
2 pages 203 to 206) is: "Duo antennarum paria." And this, as is well
known, applies to nearly all Crustacea. How well warranted are we
therefore in identifying the latter with the former. However, it is
sufficient for any one to glance at the larva of Palaemon (Figure 27)
and the Cumacean (Figure 52) in order to be convinced of their
extraordinary similarity!) The caudal portion of the embryo in the
Diastylidae, as I have recently observed, is curved upwards as in the
Isopoda, and the last pair of feet of the thorax is wanting.

Equally scanty is our knowledge of the developmental history of the
Ostracoda. We know scarcely anything except that their anterior limbs
are developed before the posterior one (Zenker). The development of
Cypris has recently been observed by Claus:--"The youngest stages are
shell-bearing Nauplius-forms."