PACKARD.] DEVELOPMENT OF PHYLLOPODS. 415 



well as its fossil allies, and tlie Eurypterida, tbe compound eyes are sessile 

 and situated on the third segment of the head, and, as we have endeav- 

 ored to show in our essay on the development of JLimulus polypliemitSj^ 

 the stalked eyes of Decapods do not represent a pair of appendages. 



v.— THE DEVELOPMENT, METAMOEPHOSES, AND GENE- 

 ALOGY OF PHYLLOPODS. 



I. — The Nauplius form in the Phyllopods. 



As introductory to the notes furnished by Dr. Gissler on the develop- 

 ment of Apus and Streptoceplialus^ we will i:)reface his remarks with 

 some account of the early phases of different Phyllopods, beginning 

 with Limnetis, as worked out by Grube.^ 



The young of this genus is a Nauplius of peculiar form, with three 

 pairs of ai)pendages, a very large carapace which covers the entire body, 

 and the edges of which are serrated. The carapace is larger than in any 

 other Phyilopod larva known, and there are two large lateral hornlike 

 projections from each side of the head in front of the iirst pair of ap- 

 pendages. The labrum is not especially developed, while in the other 

 genera it forms a characteristic feature of Phyilopod naui>lii. 



Limnetis gouldii has a nauplius of the same general shape as the 

 European species, as we have received specimens of a similar carapace 

 from Hanover, N. H. 



A quite full account of the development of Limnadia licrmanni has 

 been given by Le- 

 reboullet. Fig. 42 

 represents the 

 f r e shly-li a t c h e d 

 Nauplius, which is 

 of very primitive 

 form. The first 

 pair of antenuse 

 are in the Nau- 

 l^lius wanting, not 

 budding out until 

 near adult life. 



J-he laurum (to) Pig.42. — NaupUusofiiwrnadiaTicrw^?!?!!. cnf^ggcond antenna ;md, man- 

 is enormous and. ^^^'®; to, labrum. Much enlarged. After Lereboullet. 



very long. The carapace arises in this genus, as also in Estheria, from 

 a x)oint in the head just behind the mandibular segment. Fig. 43 rep- 

 resents the larva before the first antennae have begun to grow out. 

 The ocellus is still large and i^erforms its functions, while the abdomen 

 ends in a pair of uropoda. The development of Estheria^ as given in a 

 fragmentary way by Joly, shows that the Nauplius differs mainly from 

 that of Limnadia in the labrum being three-toothed at the end. 



Fig. 44 represents the freshly hatched larva of Apus cancrifonnis ; 

 the usual three pairs of nauplius-appendages representing the first and 

 se<iond antennse, and the mandibles of the adult are present^ while the 

 ovate body is segmented behind the mandibular segment. 



The first larval stage of Lepidurus, as worked out by Brauer (Figs. 45, 

 46), is rather different from that of Apus. The limbs are slenderer, and a 

 rudimentary carapace arises on the antennal segments, while the body 

 behind is not segmented. 



'Memoirs Boston Soc. Nat. Hist., 1872, Vol. I, pp. 174, 175. 

 ^Bemerkimgeii iiber die Phyllopoden. 



