Development of Estheria Packardi. 11 



fr om each other, but are confluent dorsally. They exhibit each 

 a distinct, narrow linguiform marking, which is the first 

 trace of the shell-gland. Behind this rudiment of the shell 

 appear on each side a regular series of 4 bud-like promin- 

 ences, which constitute the first trace of the 4 anterior pairs 

 of branchial legs. They are, as above stated, like the de- 

 veloping shell, enclosed within the larval skin, which passes 

 over them without any interruption. 



In the Nauplian limbs no perceptible change has taken 

 place, and the labrum, the ocellus and the alimentary 

 tube also exhibit the very same appearance as in the 2 pre- 

 ceding stages. 



The body has, however, now become very transparent, 

 and the differentiation of the tissues has proceeded, so as 

 to show rather distinctly the several muscles moving the 

 antennæ and mandibular feet (see fig. 6). The length of 

 the larva in this stage is 0,42 mm., and accordingly but very 

 little greater than in the preceding stage. 



Fifth larval stage. 



(PI. II, figs. 1 & 2). 



This stage is rather sharply marked off from the pre- 

 ceding one, a complete exuviation of the larva having taken 

 place, whereby both the carapace and the lateral pedal buds 

 now become freely exposed. 



The carapace has somewhat increased in size, covering 

 a greater part of the trunk, and advancing over the anterior 

 pair of pedal buds, its posterior emargination having at 

 the same time become distinctly angular. 



The furcal processes have likewise increased in length, 



2 — Archiv for Math, og Naturv. B. XVIII No. 2. 



Trykt den 6te Juni 1896. 



