PACKARD.] EELATIONS OF NEBALIA TO THE DECAPODS. 441 



geoffroyi. Unfortunately the pamphlet is in Russian, and only brief 

 abstracts of it have appeared in German. But as amj)le and well-drawn 

 ligures 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 antennas and of the mandibles bud out, the abdomen 

 also being difierentiated from the rest of the body (PI. XXXVIII, fig. 1). 

 This is regarded as representing the free nauplius condition of other 

 Crustacea. At a succeeding stage (Fig. 2) the two pairs of maxillse and 

 two xjairs of thoracic feet bud out 5 and in a stage immediately succeed- 

 ing (Fig. 3) the palpus of the mandibles elongates, the maxillae are two- 

 branched, and seven (or eight) pairs of thoracic feet are indicated. In 

 a succeeding stage (Fig. 4) IsTebalian characters assert themselves; such 

 are the carapace and large rostrum, the biramous anterior pair of an- 

 tennae, the unbranched 2d pair, the long mandibular palpus, the ab- 

 sence of any rudiments of maxillipedes, and the eight pairs of thoracic 

 feet (baenopoda) 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 maxillae 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 difierentiated from the head, may have remained afterwards 

 as a part of the thorax. An intermediate step is the retention in the 

 MysidcB of the last pair of maxillij)edes 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 JSTebalia 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 Nehalia geoffroyi of the 

 Mediterranean Sea. We have in the sections of Nehalia 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- 

 nikofl''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 ab 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 protozoea, and at length a 

 zoea 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- 



