FIRST ZOEA OF PORCELLANA. 59 



The larva immediately after its escape from the eeg, is shown 

 in Plate VI, Figure 1. It is able to rise from the bottom and to 

 swim a little by flapping its abdomen, but until the next moult it 

 spends most of its time lying nearly motionless upon the bottom. 



The carapace makes a little more than two-fifths of the total 

 length of the body, and is folded upon itself in such a way as to 

 form a well defined transverse band running: across its dorsal 



o 



surface near the posterior edge. The posterior spines of the cara- 

 pace do not seem to be at all invnginated, but they are very much 

 convoluted and wrinkled, and their free extremities are bent 

 forwards under the posterior edge of the carapace. Between the 

 eyes the anterior end of the carapace forms a protuberant rounded 

 front, and the convoluted and wrinkled rostrum is bent down 

 towards the ventral surface. The eyes lie in deep notches on the 

 anterior edge of the carapace, and they appear to be movable, 

 although the stalks are very short. 



The third pair of maxillipeds are small and rudimentary, while 

 the first, Mp, and second, Mp' , pairs are well developed, although 

 their locomotor setae are not yet protruded, and the limbs are not 

 moved but remain constantly in the position which is shown in the 

 figure. The abdomen has five free movable somites, besides the 

 sixth which is not separated from the telson, T. 



The pigment is more conspicuous at this time than during the 

 stages which follow, and consists of a number of pretty constant 

 bright red spots. One of them is on the basal portion, and one on 

 the flagellum of the second antenna, one on the mandible, M, one 

 on the basal joint of the first maxilliped, two on the basal joint of the 

 second and one on the third, as well as one about halfway between 

 the base and tip of the second; there is a long dendritic spot on 

 the posterior edge of the first, the second, the third, and the fourth 

 abdominal somite, and a pair of spots on the telson. 



The whole surface of the body is covered by a delicate embryo- 

 nic cuticle, which is too transparent to be visible with the magni- 

 fying power under which Figure 1 was drawn. This cuticle 

 conforms to the outline of the body except on the two pairs of 

 antenna? and the telson. It will be described, in detail, later, in 

 the account of the appendages. 



Some of the larva? free themselves from it within a couple of 

 hours, and assume the form shown in Plate VI, Figure 5, while 

 others do not escape from it until nearly or quite twenty-four hours 



