Chap. VII. DEVELOPMENT OF MYSIS. 65 



described in detail by Yan Beneden. So far as I Lave 

 tested tliem I can only confirm bis statements. Tbe 

 development of tbe embryo commences witb tbe forma- 

 tion of tbe tail ! This makes its appearance as a simple 

 lobe, tbe dorsal surface of wbicb is turned towards and 

 closely applied to tbat of tbe embryo. (Tbe young of 

 otber Stalk-eyed Crustacea are, as is well known, bent 

 in tbe egg in sucb a manner tbat tbe ventral surfaces 

 of tbe anterior and posterior balves of tbe body are 

 turned towards eacb otber, — in tbese, tberefore, tbe 

 dorsal, and in Mysis tbe ventral surface appears convex.) 

 Tbe tail soon acquires tbe furcate form witb wbicb we 

 made acquaintance in tbe last Prawn-Zoea described. 

 Then two pairs of tbick ensiform appendages make 

 tbeir appearance at tbe opposite end of tbe body, and 

 bebind tbese a pair of tubercles wbicb are easily over- 

 looked. Tbese are tbe antennae and mandibles. Tbe 

 egg-membrane now bursts, before any internal organ, 

 or even any tissue, except tbe cells of tbe cutaneous 

 layer, is formed. The young animal migbt be called a 

 Nauplius ; but essentially tbere is notbing but a roiigli 

 copy of a Nauplius-skin, almost like a new egg- 

 membrane, witbin wbicb tbe Mijsis is developed. Tbe 

 ten pairs of appendages of tbe fore- (maxillae, maxilli- 

 pedes) and middle-body make tbeir aj)pearance simul- 

 taneously, as do tbe five pairs of abjiominal feet at a 

 later period. Soon after tbe young Mysis casts tbe Nau- 

 plius-envelope it quits the brood-poucb of tbe mother.^^ 



^3 Van Beneden, who regards the eye-peduncles as limbs, cannot 

 however avoid remarking upon Mysis : " Ce pedicule n'apparait 



J, 



