1 882.] Repress ■: i'ocarida. 871 



at this time, in the absence of differentiation of the 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 time 

 Nebalia leaves the brood sac of the mother, it is but one step 

 removed, so to speak, from the adult form. 



MetschnikofTs observations were made on Nebalia geoffroyi o{ 

 the Mediterranean sea. We have in our sections of Nebalia bi/>es 

 observed stages of development in the young similar to the stages 

 represented by MetschnikofTs Fig. 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 MetschnikofTs Fig. 19, or Fig. 5, 

 PI. xv, they are of the same form ; the rostrum being large, the 

 procephalic lobes large, the eyes small, the stalks not yet devel- 

 oped, while the maxillary palpus stretches back to the 1st abdom- 

 inal 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 all these features we see only a 

 general 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 

 (Schizopod) Mysis.— It would appear that if Nebalia were a Deca- 

 pod, that in its larval stage it should present a close homology 

 with 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, Professor G. O. Sars has afforded us the material for 

 such a comparison. The early stages of Mysis, as worked out 

 by Van Beneden and Claparede, and of Nebalia, are much alike ; 

 the formation of the blastoderm is much the same. The nauplius 

 stage in the egg is nearly identical in both, but beyond this the 

 parallelism ceases to be an exact one ; Nebalia turns off and fol- 

 lows quite a different developmental path from Mysis or any 

 Decapod. If we compare the young of Nebalia, taken from the 

 brood-sac, with that of Mysis, as figured by Claparede (Plate 



