CHAP. VII. DEVELOPMENT OF MYSIS. 65 



described in detail by Van Beneden. So far as I have 

 tested them I can only confirm his statements. The 

 development of the embryo commences with the forma- 

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

 lobe, the dorsal surface of which is turned towards and 

 closely applied to that of the embryo. (The young of 

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

 in the egg in such a manner that the ventral surfaces 

 of the anterior and posterior halves of the body are 

 turned towards each other, in these, therefore, the 

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

 The tail soon acquires the furcate form with which we 

 made acquaintance in the last Prawn-Zoea described. 

 Then two pairs of thick ensiform appendages make 

 their appearance at the opposite end of the body, and 

 behind these a pair of tubercles which are easily over- 

 looked. These are the aritennaB and mandibles. The 

 egg-membrane now bursts, before any internal organ, 

 or even any tissue, except the cells of the cutaneous 

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

 Nauplius ; but essentially there is nothing but a rough 

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

 membrane, within which the Mysis is developed. The 

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

 pedes) and middle-body make their appearance simul- 

 taneously, as do the five pairs of abdominal feet at a 

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

 plius-envelope it quits the brood-pouch of the mother. 19 



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

 however avoid remarking upon Mysis: "Ce pe'dicule n'apparait 



F 



