REPORT ON THE CRUSTACEA MA CRURA. 915 



as the earliest is that which was described and figured by Anton Dohrn in his memoir 

 on Amphion reynaudi. 1 This he calls the Zoea form, and specimens which he procured 

 from the Hamburg Museum were 7 mm. in length. 



The specimen that I have figured (PL CXLVI. fig. 1) I believe to have been the same 

 as that which is given in fig. 73 (p. 903), from a drawing by Willemoes Suhm, and 

 examined by him while in a fresh condition. It was only 5 mm. long, and we may assume 

 it to be a younger animal than that which Dohrn has described. 



In this stage, the earliest yet known, the cephalic appendages are all in a forward 

 condition, the oral appendages in a mature form, and the two pairs of gnathopoda fully 

 developed as far as they are yet known to be. The pleon consists of only six somites, 

 and the caudal extremity is a simple spoon-like foliaceous plate, fringed with- a few hairs. 



Fig. 2z in the same plate represents the caudal extremity of another specimen that 

 has attained the length of 6 mm., in which no degree of progressive growth is observable, 

 excepting that the sixth pair of pereiopoda is seen to be taking form within the integu- 

 mental structure, but is not yet developed as a free appendage. Dohrn's specimen is 

 7 mm. long, and at this stage as shown by him, 2 the first pair of pereiopoda or third pair 

 of appendages are in the course of development in the form of a pair of curved saccular 

 appendages, and the caudal extremity has undergone a great change in the development 

 of the sixth pair of pleopoda as the lateral appendages of the rhipidura, while the telson 

 still retains the broad and foliaceous condition of the earlier known Zoea stage. 



Fig. 3 in PL CXLVI. represents a specimen that has progressed a little further, 

 and shows the third pair of appendages or first pair of pereiopoda developed; the 

 rhipidura is more advanced by the telson being produced in a narrow and tapering 

 form instead of being broad and foliaceous as in Dohrn's specimen. 



On PL CXLVI. fig. 4, one is seen to have the second pair of pereiopoda (/) or fourth 

 pair of appendages in an early stage of development, in the saccular stage, while in 

 fig. 5 on the same plate the same pair of appendages is shown in a still more advanced 

 form, being biramose and saccular. The rhipidura is increasing in the adult characters, 

 but as yet the telson though broad is reduced to a tapering and foliaceous condition. 



One specimen, 11 mm. long, was taken in the Western Pacific, in which the four pairs 

 of legs are fully developed, but I have not thought it necessary to figure it because it so 

 closely resembled fig. 1 on PL CXLVIL, except for the presence in the latter of two more 

 pairs of legs. 



One specimen with five well-developed pairs of legs was taken in the West Pacific 



1 Loc. cit., pi. xvi. fig. 11. 2 Loc. cit., p. 174, pi. xvi. fig. 10. 



