400 Transactions. 



Larval Stages. 



There are four well-marked stages known in the life-history of Jasus 

 lalandii, which might briefly be noted as — (a) the naupliosotna, a form 

 swimming rapidly by means of the antennae ; (b) the phyllosoma, which 

 swims more slowly, and uses the exopods of the thoracic legs ; (c) the 

 " natant " stage, or puerulus, which either walks about the bottom, or 

 swims by means of the abdominal pleopods, which are specially hooked 

 together for the purpose ; and (d) the adult, which makes use of the telson 

 and uropods occasionally for swimming.* 



1 have had for examination specimens of the three larval stages of 

 J. lalandii, and the following notes will be in the form of brief descriptions 

 of them. The first two stages— the naupliosoma and the phyllosoma — 

 are described from specimens reared by Mr. T. Anderton, of the Portobello 

 Marine Fish-hatchery, Dunedin ; and the pueruli were collected at Stewart 

 Island by Mr. Walter Traill. I have also a specimen of the puerulus 

 of J. hiigelii, collected at Cuvier Island, near Auckland, by Mr. P. W. 

 Grenfell. All the specimens were in the possession of Dr. Chilton, who 

 very kindly forwarded it to me to describe in this paper. 



{a.) The Naupliosonm'{fLg. 1). 



The naupliosoma larva has only recently been described by Gilchrist 

 (1913, p. 225)t, who observed it hatching from specimens of Jasus lalandii 

 kept in tanks. This stage lasted only a very short time (four to six hours), 

 and would, he said, be readily overlooked, especially if hatching takes 

 place in the night. In the letter accompanying the specimens I have 

 Mr. Anderton wrote that the stage with setae-bearing antennae could not 

 be found after an hour or more. 



The naupliosoma is a much more advanced stage than the nauplius, 

 though it resembles it in the possession of large biramose and setose 

 antennae, and a median eye-spot. In it the mouth parts are all well 

 developed, except the 1st maxillipedes, which are rudimentary ; there is 

 a distinct thorax, bearing 3 pairs of biramose walking-legs, and a short, 

 indefinitely segmented abdomen is also present. 



The cephalic region is roimded, and is nearly as deep from above down- 

 wards as it is long and broad ; it is rendered opaque by the presence of 

 yolk-granules. 



The antennules, of normal length, project between the eyes. The 

 antennae are large, consisting of a fairly long basal portion, bearing a 

 protuberance posteriorly at the point of origin ; they divide without visible 

 segmentation into a longer exopod, bearing 7 setose processes, and a shorter 

 endopod, with only 2 processes ; 2 spines project into the two processes 

 which arise at the tip of both endopod and exopod. 



* In the proceedings of the Linnean Society's meeting of the 2nd March, 1916, there 

 is an abstract of a paper by Dr. Gilchrist on '■ Lai-val and Post-larval Stages of Jasus 

 lalandii." Dr. Gilchrist is now of the opinion that the term naupliosoma, which he 

 applied to the first stage was rather inappropriate, " since it tends to obscure the 

 reasonable presumption that the nauplius stage has ' been passed long before in the 

 development of the embryo.' " The interesting and important information given in 

 Dr. Gilchrist's paper will no doubt be soon available in complete form in the publi- 

 cations of the Linnean Society. 



t Since the above was written my attention has been called to a description of this 

 stage by G. M. Thomson (Trans. N.Z". Inst., vol. 39. 1907, p. 484, pi. 20). In the same 

 place the above author has also described the phyllosoma, and gave a drawing of this 

 second stage. 



