PACKARD.] RELATIONS OF NEBALIA TO THE DECAPODS. AA1 
geoffroyi. Unfortunately the pamphlet is in Russian, and only brief 
abstracts of it have appeared in German. But as ample and well-drawn 
figures illustrate the work we can state the salient points in the on- 
togeny of this interesting Crustacean. The yolk does not undergo total 
division, but by the subdivision of a large polar cell the yolk becomes 
surrounded by a layer of blastodermic cells. Soon after the rudiments 
of the two pairs of antenne and of the mandibles bud out, the abdomen 
also being differentiated from the rest of the body (Pl. XX X VIIL fig. 1). 
This is regarded as representing the free nauplius condition of other 
Crustacea. At a succeeding stage (Fig. 2) the two pairs of maxille and 
two pairs of thoracic feet bud out; and in a’stage immediately succeed- 
ing (Fig. 3) the palpus of the mandibles elongates, the maxille are two- 
branched, and seven (or eight) pairs of thoracic feet are indicated. In 
a succeeding stage (Fig. 4) Nebalian characters assert themselves; such 
are the carapace and large rostrum, the biramous anterior pair of an- 
tenne, the unbranched’ 2d pair, the long mandibular palpus, the ab- 
sence of any rudiments of maxillipedes, and the eight pairs of thoracic 
feet (beenopoda) and three pairs of abdominal feet (uropoda), all of 
which are now well developed. At this stage it may be seen that, as 
in spiders, the 1st pair of thoracic feet may represent the 2d maxille of 
insects transferred from the head to the thorax; so in Nebalia, the 
three first of the eight pairs of thoracic feet’ may correspond to the 
three pairs of maxillipedes of Decapods, which in early life, before the 
thorax is differentiated from the head, may have remained afterwards 
as a part of the thorax. An intermediate step is the retention in the 
Myside of the last pair of maxillipedes or the 1st pair of thoracic feet, 
so that these Crustacea have six pairs of feet. Moreover Nebalia at 
this time, in the absence of differentiation of thorax from the abdomen, 
and of thoracic and abdominal feet, the two sets being similar in form 
and development to each other, may also represent the Phyllopod stage. 
In the next stage, at the the time Nebalia leaves the brood sac of the 
mother, it is but one step removed, so to speak, from the adult form. 
Metschnikoff’s observations were made on Nebalia geoffroyi of the 
Mediterranean Sea. We have in the sections of Nebalia bipes observed 
stages of development in the young similar to the stages represented by 
Metschnikoff’s figure 13 or 14, and have found in the bottom of the 
vial in which the specimens were sent several young which had fallen 
out of the brood sac of the parent. Upon comparing these with Metsch- 
nikofft’s Fig. 19, or Fig. 68, in text, they are of the same form; the rostrum 
being large, the procephalic lobes large, the eyes small, the stalks not 
yet developed, while the maxillary palpus stretches back to the 1st 
abdominal feet; the thoracic feet are covered by the large carapace; 
and a 4th pair of abdominal feet have developed, while the caudal ap- 
pendages are as in the adult. In ali these features we see only a gen- 
eral resemblance to the Schizopods of any value, the similar earliest 
phases of development proving of no special importance. 
Comparison between the early stages of Nebalia and the Decapod (Schizo- 
pod) Mysis.—It would appear that if Nebalia were a Decapod that in its 
larval stage it should present a close homology with the Schizopods at 
a similar stage of existence. In Euphausia the young leaves the egg and 
becomes a free swimming nauplius, and then a protozoéa, and at length a 
zoéa larva before assuming the adult condition. It is evident that since 
Nebalia passes its early stages in the incubatory pouch of the mother, 
that it should be rather compared with the young, when about ready to 
leave the mother, of some Mysis-like form. 
Happily Prof. G. O. Sars has afforded us the material for such a com- 
