Dr. F. Miiller on the Metamorphoses of the Praims. 105 



mediate feet have two bristles at the apex of the anterior branch, 

 and six on the anterior margin and apex of the posterior branch ; 

 and each branch of the posterior feet has two bristles at its apex 

 and one below this point. 



The little animal is rather opaque, and of a brownish colour, 

 which is more strongly marked at the apices of the feet. The 

 structure of the mouth and of the internal organs was not ob- 

 served. 



The somewhat flexible feet, with their few long bristles, form 

 no very effective motory apparatus. A man floating perpendi- 

 cularly in the water, with widespread arms and slender willow- 

 branches in each hand, striving to work himself upward, would 

 furnish a notion of the peculiar movement by which this Nauplnts 

 and the Zoea proceeding from it may be recognized at the first 

 glance amongst hundreds of other small Crustacea*. 



In a rather larger larva (0*5 mill, in length), taken on the 

 13th (»f January, which agreed in the general form of the body, 

 in the structure of the feet, and in colour with the preceding 

 one, the posterior extremity was drawn out into two thick conical 

 processes, at the apices of which stood the two long caudal 

 bristles, each accompanied on the inside by two and on the 

 outside by three shorter and partly spiniform bristles. The 

 number of bristles on the intermediate feet had also increased. 

 As the first indication of the carapace, a transverse fold ran 

 across the back, nearly in the middle of the body. The poste- 

 rior feet were placed more anteriorly and nearer the median 

 line, towards the mouth, which is situated between them ; be- 

 fore the mouth, between the intermediate feet, was a large helmet- 

 8ha])ed upper lip. The short stem of these feet had become 

 thickened almost into a globular form ; some new part was 

 evidently being formed in its interior, the outlines of which, 

 however, were not yet distinct. Behind the mouth, and filling 

 the median third of the body, four pairs of long and plump 

 lobes had sprouted from the ventral surface, and, inclming 

 backwards, had applied themselves to the body. In the form of 

 the first two pairs the future lower jaws could already be re- 

 cognized. 



This larva is closely approached by four others, probably be- 

 longing to the same swarm, which were taken at the same time 

 (24th of January). In the swelling at the base of the posterior 



• From thi« peculiar movement, observed with the naked e\*e, I recojj- 

 nized the little animal just described as the larva of Peneus; microscopic 

 examination made this opinion appear, if not erroneous, at least extremely 

 improbable. A month later, intermediate forms occurred which showed 

 the naked eve to have been right, in opposition to the microscope ; the 

 latter alone would probably never have led me to suspect the true nature 

 of my Sauplius. 



